网络协议栈实现分析5--INET socket 层分析
INET socket 层分析
INET层实现功能：主要实现INET socket套接字，例如（inet_create,inet_bind,inet_accept等），它是实现BSD层的接口函数，这些函数完成相应的检查工作后继续将请求发送给下层传输层函数进行具体的处理。其中涉及主要文件有net/inet/af_inet.c
文件：af_inet.c
#include <linux/config.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <asm/segment.h>
#include <asm/system.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include "ip.h"
#include "protocol.h"
#include "arp.h"
#include "rarp.h"
#include "route.h"
#include "tcp.h"
#include "udp.h"
#include <linux/skbuff.h>
#include "sock.h"
#include "raw.h"
#include "icmp.h"
#define min(a,b) ((a)<(b)?(a):(b))
extern struct proto packet_prot;
/*
* See if a socket number is in use.
*/
//检测端口号，端口使用返回1，否则返回0
static int sk_inuse(struct proto *prot, int num)
{
struct sock *sk;
for(sk = prot->sock_array[num & (SOCK_ARRAY_SIZE -1 )];
sk != NULL; sk=sk->next)
{
if (sk->num == num)
return(1);
}
return(0);
}
/*
* Pick a new socket number
*/
unsigned short get_new_socknum(struct proto *prot, unsigned short base)
{
static int start=0;
/*
* Used to cycle through the port numbers so the
* chances of a confused connection drop.
*/
int i, j;
int best = 0;
int size = 32767; /* a big num. */
struct sock *sk;
if (base == 0)
base = PROT_SOCK+1+(start % 1024);
if (base <= PROT_SOCK)
{
base += PROT_SOCK+(start % 1024);
}
/* Now look through the entire array and try to find an empty ptr. */
for(i=0; i < SOCK_ARRAY_SIZE; i++)
{
j = 0;
sk = prot->sock_array[(i+base+1) &(SOCK_ARRAY_SIZE -1)];
while(sk != NULL)
{
sk = sk->next;
j++;
}
if (j == 0)
{
start =(i+1+start )%1024;
return(i+base+1);
}
if (j < size)
{
best = i;
size = j;
}
}
/* Now make sure the one we want is not in use. */
while(sk_inuse(prot, base +best+1))
{
best += SOCK_ARRAY_SIZE;
}
return(best+base+1);
}
/*
* Add a socket into the socket tables by number.
*/
//加入一个有端口号的sock结构到 sock_array[]中
void put_sock(unsigned short num, struct sock *sk)
{
struct sock *sk1;
struct sock *sk2;
int mask;
unsigned long flags;
sk->num = num;
sk->next = NULL;
num = num &(SOCK_ARRAY_SIZE -1);
/* We can't have an interrupt re-enter here. */
save_flags(flags);
cli();
sk->prot->inuse += 1;
if (sk->prot->highestinuse < sk->prot->inuse)
sk->prot->highestinuse = sk->prot->inuse;
if (sk->prot->sock_array[num] == NULL)
{
sk->prot->sock_array[num] = sk;
restore_flags(flags);
return;
}
restore_flags(flags);
for(mask = 0xff000000; mask != 0xffffffff; mask = (mask >> 8) | mask)
{
if ((mask & sk->saddr) &&
(mask & sk->saddr) != (mask & 0xffffffff))
{
mask = mask << 8;
break;
}
}
cli();
sk1 = sk->prot->sock_array[num];
for(sk2 = sk1; sk2 != NULL; sk2=sk2->next)
{
if (!(sk2->saddr & mask))
{
if (sk2 == sk1)
{
sk->next = sk->prot->sock_array[num];
sk->prot->sock_array[num] = sk;
sti();
return;
}
sk->next = sk2;
sk1->next= sk;
sti();
return;
}
sk1 = sk2;
}
/* Goes at the end. */
sk->next = NULL;
sk1->next = sk;
sti();
}
/*
* Remove a socket from the socket tables.
*/
//删除一个指定的sock结构
static void remove_sock(struct sock *sk1)
{
struct sock *sk2;
unsigned long flags;
if (!sk1->prot)
{
printk("sock.c: remove_sock: sk1->prot == NULL/n");
return;
}
/* We can't have this changing out from under us. */
save_flags(flags);
cli();
sk2 = sk1->prot->sock_array[sk1->num &(SOCK_ARRAY_SIZE -1)];
if (sk2 == sk1)
{
sk1->prot->inuse -= 1;
sk1->prot->sock_array[sk1->num &(SOCK_ARRAY_SIZE -1)] = sk1->next;
restore_flags(flags);
return;
}
while(sk2 && sk2->next != sk1)
{
sk2 = sk2->next;
}
if (sk2)
{
sk1->prot->inuse -= 1;
sk2->next = sk1->next;
restore_flags(flags);
return;
}
restore_flags(flags);
}
/*
* Destroy an AF_INET socket
*/
void destroy_sock(struct sock *sk)
{
struct sk_buff *skb;
sk->inuse = 1; /* just to be safe. */
/* In case it's sleeping somewhere. */
if (!sk->dead)
sk->write_space(sk);
remove_sock(sk);
/* Now we can no longer get new packets. */
delete_timer(sk);
/* Nor send them */
del_timer(&sk->retransmit_timer);
while ((skb = tcp_dequeue_partial(sk)) != NULL) {
IS_SKB(skb);
kfree_skb(skb, FREE_WRITE);
}
/* Cleanup up the write buffer. */
while((skb = skb_dequeue(&sk->write_queue)) != NULL) {
IS_SKB(skb);
kfree_skb(skb, FREE_WRITE);
}
/*
* Don't discard received data until the user side kills its
* half of the socket.
*/
if (sk->dead)
{
while((skb=skb_dequeue(&sk->receive_queue))!=NULL)
{
/*
* This will take care of closing sockets that were
* listening and didn't accept everything.
*/
if (skb->sk != NULL && skb->sk != sk)
{
IS_SKB(skb);
skb->sk->dead = 1;
skb->sk->prot->close(skb->sk, 0);
}
IS_SKB(skb);
kfree_skb(skb, FREE_READ);
}
}
/* Now we need to clean up the send head. */
cli();
for(skb = sk->send_head; skb != NULL; )
{
struct sk_buff *skb2;
/*
* We need to remove skb from the transmit queue,
* or maybe the arp queue.
*/
if (skb->next && skb->prev) {
/* printk("destroy_sock: unlinked skb/n");*/
IS_SKB(skb);
skb_unlink(skb);
}
skb->dev = NULL;
skb2 = skb->link3;
kfree_skb(skb, FREE_WRITE);
skb = skb2;
}
sk->send_head = NULL;
sti();
/* And now the backlog. */
while((skb=skb_dequeue(&sk->back_log))!=NULL)
{
/* this should never happen. */
/* printk("cleaning back_log/n");*/
kfree_skb(skb, FREE_READ);
}
/* Now if it has a half accepted/ closed socket. */
if (sk->pair)
{
sk->pair->dead = 1;
sk->pair->prot->close(sk->pair, 0);
sk->pair = NULL;
}
/*
* Now if everything is gone we can free the socket
* structure, otherwise we need to keep it around until
* everything is gone.
*/
if (sk->dead && sk->rmem_alloc == 0 && sk->wmem_alloc == 0)
{
kfree_s((void *)sk,sizeof(*sk));
}
else
{
/* this should never happen. */
/* actually it can if an ack has just been sent. */
sk->destroy = 1;
sk->ack_backlog = 0;
sk->inuse = 0;
reset_timer(sk, TIME_DESTROY, SOCK_DESTROY_TIME);
}
}
/*
* The routines beyond this point handle the behaviour of an AF_INET
* socket object. Mostly it punts to the subprotocols of IP to do
* the work.
*/
//设置和获取套接字相关信息
static int inet_fcntl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
struct sock *sk;
sk = (struct sock *) sock->data; //void * 可以转换层任何指针类型
switch(cmd)
{
//设置套接字信息
case F_SETOWN:
/*
* This is a little restrictive, but it's the only
* way to make sure that you can't send a sigurg to
* another process.
*/
if (!suser() && current->pgrp != -arg &&
current->pid != arg) return(-EPERM);
sk->proc = arg;
return(0);
//获得套接字信息
case F_GETOWN:
return(sk->proc);
default:
return(-EINVAL);
}
}
/*
* Set socket options on an inet socket.
*/
static int inet_setsockopt(struct socket *sock, int level, int optname,
char *optval, int optlen)
{
struct sock *sk = (struct sock *) sock->data;
if (level == SOL_SOCKET)
return sock_setsockopt(sk,level,optname,optval,optlen);
if (sk->prot->setsockopt==NULL)
return(-EOPNOTSUPP);
else
return sk->prot->setsockopt(sk,level,optname,optval,optlen);
}
/*
* Get a socket option on an AF_INET socket.
*/
static int inet_getsockopt(struct socket *sock, int level, int optname,
char *optval, int *optlen)
{
struct sock *sk = (struct sock *) sock->data;
if (level == SOL_SOCKET)
return sock_getsockopt(sk,level,optname,optval,optlen);
if(sk->prot->getsockopt==NULL)
return(-EOPNOTSUPP);
else
return sk->prot->getsockopt(sk,level,optname,optval,optlen);
}
/*
* Automatically bind an unbound socket.
*/
static int inet_autobind(struct sock *sk)
{
/* We may need to bind the socket. */
if (sk->num == 0)
{ //获得未使用的端口号
sk->num = get_new_socknum(sk->prot, 0);
if (sk->num == 0)
return(-EAGAIN);
//把该sock放入队列中
put_sock(sk->num, sk);
//dummy_th是tcp首部，source是本地端口号，ntohs使用网络字节序
sk->dummy_th.source = ntohs(sk->num);
}
return 0;
}
/*
* Move a socket into listening state.
*/
//对于系统调用到这一层L5就结束了
static int inet_listen(struct socket *sock, int backlog)
{
struct sock *sk = (struct sock *) sock->data;
if(inet_autobind(sk)!=0)
return -EAGAIN;
/* We might as well re use these. */
/*
* note that the backlog is "unsigned char", so truncate it
* somewhere. We might as well truncate it to what everybody
* else does..
*/
if ((unsigned) backlog > 128)
backlog = 128;
sk->max_ack_backlog = backlog;
if (sk->state != TCP_LISTEN)
{
sk->ack_backlog = 0;
sk->state = TCP_LISTEN; //这里是关键
}
return(0);
}
/*
* Default callbacks for user INET sockets. These just wake up
* the user owning the socket.
*/
static void def_callback1(struct sock *sk)
{
if(!sk->dead)
wake_up_interruptible(sk->sleep);
}
static void def_callback2(struct sock *sk,int len)
{
if(!sk->dead)
{
wake_up_interruptible(sk->sleep);
sock_wake_async(sk->socket, 1);
}
}
static void def_callback3(struct sock *sk)
{
if(!sk->dead)
{
wake_up_interruptible(sk->sleep);
sock_wake_async(sk->socket, 2);
}
}
/*
* Create an inet socket.
*
* FIXME: Gcc would generate much better code if we set the parameters
* up in in-memory structure order. Gcc68K even more so
*/
//inet 层sock结构的创建和初始化
static int inet_create(struct socket *sock, int protocol)
{
struct sock *sk;
struct proto *prot;
int err;
sk = (struct sock *) kmalloc(sizeof(*sk), GFP_KERNEL);
if (sk == NULL)
return(-ENOBUFS);
sk->num = 0;
sk->reuse = 0;
switch(sock->type)
{
case SOCK_STREAM:
case SOCK_SEQPACKET:
if (protocol && protocol != IPPROTO_TCP)
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPROTONOSUPPORT);
}
protocol = IPPROTO_TCP;
sk->no_check = TCP_NO_CHECK;
prot = &tcp_prot;
break;
case SOCK_DGRAM:
if (protocol && protocol != IPPROTO_UDP)
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPROTONOSUPPORT);
}
protocol = IPPROTO_UDP;
sk->no_check = UDP_NO_CHECK;
prot=&udp_prot;
break;
case SOCK_RAW:
if (!suser())
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPERM);
}
if (!protocol)
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPROTONOSUPPORT);
}
prot = &raw_prot;
sk->reuse = 1;
sk->no_check = 0; /*
* Doesn't matter no checksum is
* performed anyway.
*/
sk->num = protocol;
break;
case SOCK_PACKET:
if (!suser())
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPERM);
}
if (!protocol)
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPROTONOSUPPORT);
}
prot = &packet_prot;
sk->reuse = 1;
sk->no_check = 0; /* Doesn't matter no checksum is
* performed anyway.
*/
sk->num = protocol;
break;
default:
kfree_s((void *)sk, sizeof(*sk));
return(-ESOCKTNOSUPPORT);
}
sk->socket = sock;
#ifdef CONFIG_TCP_NAGLE_OFF
sk->nonagle = 1;
#else
sk->nonagle = 0;
#endif
sk->type = sock->type;
sk->stamp.tv_sec=0;
sk->protocol = protocol;
sk->wmem_alloc = 0;
sk->rmem_alloc = 0;
sk->sndbuf = SK_WMEM_MAX;
sk->rcvbuf = SK_RMEM_MAX;
sk->pair = NULL;
sk->opt = NULL;
sk->write_seq = 0;
sk->acked_seq = 0;
sk->copied_seq = 0;
sk->fin_seq = 0;
sk->urg_seq = 0;
sk->urg_data = 0;
sk->proc = 0;
sk->rtt = 0; /*TCP_WRITE_TIME << 3;*/
sk->rto = TCP_TIMEOUT_INIT; /*TCP_WRITE_TIME*/
sk->mdev = 0;
sk->backoff = 0;
sk->packets_out = 0;
sk->cong_window = 1; /* start with only sending one packet at a time. */
sk->cong_count = 0;
sk->ssthresh = 0;
sk->max_window = 0;
sk->urginline = 0;
sk->intr = 0;
sk->linger = 0;
sk->destroy = 0;
sk->priority = 1;
sk->shutdown = 0;
sk->keepopen = 0;
sk->zapped = 0;
sk->done = 0;
sk->ack_backlog = 0;
sk->window = 0;
sk->bytes_rcv = 0;
sk->state = TCP_CLOSE;
sk->dead = 0;
sk->ack_timed = 0;
sk->partial = NULL;
sk->user_mss = 0;
sk->debug = 0;
/* this is how many unacked bytes we will accept for this socket. */
sk->max_unacked = 2048; /* needs to be at most 2 full packets. */
/* how many packets we should send before forcing an ack.
if this is set to zero it is the same as sk->delay_acks = 0 */
sk->max_ack_backlog = 0;
sk->inuse = 0;
sk->delay_acks = 0;
skb_queue_head_init(&sk->write_queue);
skb_queue_head_init(&sk->receive_queue);
sk->mtu = 576;
sk->prot = prot;
sk->sleep = sock->wait;
sk->daddr = 0;
sk->saddr = 0 /* ip_my_addr() */;
sk->err = 0;
sk->next = NULL;
sk->pair = NULL;
sk->send_tail = NULL;
sk->send_head = NULL;
sk->timeout = 0;
sk->broadcast = 0;
sk->localroute = 0;
init_timer(&sk->timer);
init_timer(&sk->retransmit_timer);
sk->timer.data = (unsigned long)sk;
sk->timer.function = &net_timer;
skb_queue_head_init(&sk->back_log);
sk->blog = 0;
sock->data =(void *) sk;
sk->dummy_th.doff = sizeof(sk->dummy_th)/4;
sk->dummy_th.res1=0;
sk->dummy_th.res2=0;
sk->dummy_th.urg_ptr = 0;
sk->dummy_th.fin = 0;
sk->dummy_th.syn = 0;
sk->dummy_th.rst = 0;
sk->dummy_th.psh = 0;
sk->dummy_th.ack = 0;
sk->dummy_th.urg = 0;
sk->dummy_th.dest = 0;
sk->ip_tos=0;
sk->ip_ttl=64;
#ifdef CONFIG_IP_MULTICAST
sk->ip_mc_loop=1;
sk->ip_mc_ttl=1;
*sk->ip_mc_name=0;
sk->ip_mc_list=NULL;
#endif
sk->state_change = def_callback1;
sk->data_ready = def_callback2;
sk->write_space = def_callback3;
sk->error_report = def_callback1;
if (sk->num)
{
/*
* It assumes that any protocol which allows
* the user to assign a number at socket
* creation time automatically
* shares.
*/
put_sock(sk->num, sk);
sk->dummy_th.source = ntohs(sk->num);
}
if (sk->prot->init)
{
err = sk->prot->init(sk);
if (err != 0)
{
destroy_sock(sk);
return(err);
}
}
return(0);
}
/*
* Duplicate a socket.
*/
static int inet_dup(struct socket *newsock, struct socket *oldsock)
{
return(inet_create(newsock,((struct sock *)(oldsock->data))->protocol));
}
/*
* Return 1 if we still have things to send in our buffers.
*/
static inline int closing(struct sock * sk)
{
switch (sk->state) {
case TCP_FIN_WAIT1:
case TCP_CLOSING:
case TCP_LAST_ACK:
return 1;
}
return 0;
}
/*
* The peer socket should always be NULL (or else). When we call this
* function we are destroying the object and from then on nobody
* should refer to it.
*/
static int inet_release(struct socket *sock, struct socket *peer)
{
struct sock *sk = (struct sock *) sock->data;
if (sk == NULL)
return(0);
sk->state_change(sk);
/* Start closing the connection. This may take a while. */
#ifdef CONFIG_IP_MULTICAST
/* Applications forget to leave groups before exiting */
ip_mc_drop_socket(sk);
#endif
/*
* If linger is set, we don't return until the close
* is complete. Other wise we return immediately. The
* actually closing is done the same either way.
*
* If the close is due to the process exiting, we never
* linger..
*/
if (sk->linger == 0 || (current->flags & PF_EXITING))
{
sk->prot->close(sk,0);
sk->dead = 1;
}
else
{
sk->prot->close(sk, 0);
cli();
if (sk->lingertime)
current->timeout = jiffies + HZ*sk->lingertime;
while(closing(sk) && current->timeout>0)
{
interruptible_sleep_on(sk->sleep);
if (current->signal & ~current->blocked)
{
break;
#if 0
/* not working now - closes can't be restarted */
sti();
current->timeout=0;
return(-ERESTARTSYS);
#endif
}
}
current->timeout=0;
sti();
sk->dead = 1;
}
sk->inuse = 1;
/* This will destroy it. */
sock->data = NULL;
release_sock(sk);
sk->socket = NULL;
return(0);
}
/* this needs to be changed to disallow
the rebinding of sockets. What error
should it return? */
static int inet_bind(struct socket *sock, struct sockaddr *uaddr,
int addr_len)
{
struct sockaddr_in *addr=(struct sockaddr_in *)uaddr;
struct sock *sk=(struct sock *)sock->data, *sk2;
unsigned short snum = 0 /* Stoopid compiler.. this IS ok */;
int chk_addr_ret;
/* check this error. */
if (sk->state != TCP_CLOSE)
return(-EIO);
if(addr_len<sizeof(struct sockaddr_in))
return -EINVAL;
if(sock->type != SOCK_RAW)
{
if (sk->num != 0)
return(-EINVAL);
snum = ntohs(addr->sin_port);
/*
* We can't just leave the socket bound wherever it is, it might
* be bound to a privileged port. However, since there seems to
* be a bug here, we will leave it if the port is not privileged.
*/
if (snum == 0)
{
snum = get_new_socknum(sk->prot, 0);
}
if (snum < PROT_SOCK && !suser())
return(-EACCES);
}
chk_addr_ret = ip_chk_addr(addr->sin_addr.s_addr);
if (addr->sin_addr.s_addr != 0 && chk_addr_ret != IS_MYADDR && chk_addr_ret != IS_MULTICAST)
return(-EADDRNOTAVAIL); /* Source address MUST be ours! */
if (chk_addr_ret || addr->sin_addr.s_addr == 0)
sk->saddr = addr->sin_addr.s_addr;
if(sock->type != SOCK_RAW)
{
/* Make sure we are allowed to bind here. */
cli();
for(sk2 = sk->prot->sock_array[snum & (SOCK_ARRAY_SIZE -1)];
sk2 != NULL; sk2 = sk2->next)
{
/* should be below! */
if (sk2->num != snum)
continue;
if (!sk->reuse)
{
sti();
return(-EADDRINUSE);
}
if (sk2->num != snum)
continue; /* more than one */
if (sk2->saddr != sk->saddr)
continue; /* socket per slot ! -FB */
if (!sk2->reuse || sk2->state==TCP_LISTEN)
{
sti();
return(-EADDRINUSE);
}
}
sti();
remove_sock(sk);
put_sock(snum, sk);
sk->dummy_th.source = ntohs(sk->num);
sk->daddr = 0;
sk->dummy_th.dest = 0;
}
return(0);
}
/*
* Handle sk->err properly. The cli/sti matter.
*/
static int inet_error(struct sock *sk)
{
unsigned long flags;
int err;
save_flags(flags);
cli();
err=sk->err;
sk->err=0;
restore_flags(flags);
return -err;
}
/*
* Connect to a remote host. There is regrettably still a little
* TCP 'magic' in here.
*/
static int inet_connect(struct socket *sock, struct sockaddr * uaddr,
int addr_len, int flags)
{
struct sock *sk=(struct sock *)sock->data;
int err;
sock->conn = NULL;
if (sock->state == SS_CONNECTING && tcp_connected(sk->state))
{
sock->state = SS_CONNECTED;
/* Connection completing after a connect/EINPROGRESS/select/connect */
return 0; /* Rock and roll */
}
if (sock->state == SS_CONNECTING && sk->protocol == IPPROTO_TCP && (flags & O_NONBLOCK)) {
if (sk->err != 0)
{
err=sk->err;
sk->err=0;
return -err;
}
return -EALREADY; /* Connecting is currently in progress */
}
if (sock->state != SS_CONNECTING)
{
/* We may need to bind the socket. */
if(inet_autobind(sk)!=0)
return(-EAGAIN);
if (sk->prot->connect == NULL)
return(-EOPNOTSUPP);
err = sk->prot->connect(sk, (struct sockaddr_in *)uaddr, addr_len);
if (err < 0)
return(err);
sock->state = SS_CONNECTING;
}
if (sk->state > TCP_FIN_WAIT2 && sock->state==SS_CONNECTING)
{
sock->state=SS_UNCONNECTED;
cli();
err=sk->err;
sk->err=0;
sti();
return -err;
}
if (sk->state != TCP_ESTABLISHED &&(flags & O_NONBLOCK))
return(-EINPROGRESS);
cli(); /* avoid the race condition */
while(sk->state == TCP_SYN_SENT || sk->state == TCP_SYN_RECV)
{
interruptible_sleep_on(sk->sleep);
if (current->signal & ~current->blocked)
{
sti();
return(-ERESTARTSYS);
}
/* This fixes a nasty in the tcp/ip code. There is a hideous hassle with
icmp error packets wanting to close a tcp or udp socket. */
if(sk->err && sk->protocol == IPPROTO_TCP)
{
sti();
sock->state = SS_UNCONNECTED;
err = -sk->err;
sk->err=0;
return err; /* set by tcp_err() */
}
}
sti();
sock->state = SS_CONNECTED;
if (sk->state != TCP_ESTABLISHED && sk->err)
{
sock->state = SS_UNCONNECTED;
err=sk->err;
sk->err=0;
return(-err);
}
return(0);
}
static int inet_socketpair(struct socket *sock1, struct socket *sock2)
{
return(-EOPNOTSUPP);
}
/*
* Accept a pending connection. The TCP layer now gives BSD semantics.
*/
static int inet_accept(struct socket *sock, struct socket *newsock, int flags)
{
struct sock *sk1, *sk2;
int err;
sk1 = (struct sock *) sock->data;
/*
* We've been passed an extra socket.
* We need to free it up because the tcp module creates
* its own when it accepts one.
*/
if (newsock->data)
{
struct sock *sk=(struct sock *)newsock->data;
newsock->data=NULL;
sk->dead = 1;
destroy_sock(sk);
}
if (sk1->prot->accept == NULL)
return(-EOPNOTSUPP);
/* Restore the state if we have been interrupted, and then returned. */
if (sk1->pair != NULL )
{
sk2 = sk1->pair;
sk1->pair = NULL;
}
else
{
sk2 = sk1->prot->accept(sk1,flags);
if (sk2 == NULL)
{
if (sk1->err <= 0)
printk("Warning sock.c:sk1->err <= 0. Returning non-error./n");
err=sk1->err;
sk1->err=0;
return(-err);
}
}
newsock->data = (void *)sk2;
sk2->sleep = newsock->wait;
sk2->socket = newsock;
newsock->conn = NULL;
if (flags & O_NONBLOCK)
return(0);
cli(); /* avoid the race. */
while(sk2->state == TCP_SYN_RECV)
{
interruptible_sleep_on(sk2->sleep);
if (current->signal & ~current->blocked)
{
sti();
sk1->pair = sk2;
sk2->sleep = NULL;
sk2->socket=NULL;
newsock->data = NULL;
return(-ERESTARTSYS);
}
}
sti();
if (sk2->state != TCP_ESTABLISHED && sk2->err > 0)
{
err = -sk2->err;
sk2->err=0;
sk2->dead=1; /* ANK */
destroy_sock(sk2);
newsock->data = NULL;
return(err);
}
newsock->state = SS_CONNECTED;
return(0);
}
/*
* This does both peername and sockname.
*/
static int inet_getname(struct socket *sock, struct sockaddr *uaddr,
int *uaddr_len, int peer)
{
struct sockaddr_in *sin=(struct sockaddr_in *)uaddr;
struct sock *sk;
sin->sin_family = AF_INET;
sk = (struct sock *) sock->data;
if (peer)
{
if (!tcp_connected(sk->state))
return(-ENOTCONN);
sin->sin_port = sk->dummy_th.dest;
sin->sin_addr.s_addr = sk->daddr;
}
else
{
sin->sin_port = sk->dummy_th.source;
if (sk->saddr == 0)
sin->sin_addr.s_addr = ip_my_addr();
else
sin->sin_addr.s_addr = sk->saddr;
}
*uaddr_len = sizeof(*sin);
return(0);
}
/*
* The assorted BSD I/O operations
*/
static int inet_recvfrom(struct socket *sock, void *ubuf, int size, int noblock,
unsigned flags, struct sockaddr *sin, int *addr_len )
{
struct sock *sk = (struct sock *) sock->data;
if (sk->prot->recvfrom == NULL)
return(-EOPNOTSUPP);
if(sk->err)
return inet_error(sk);
/* We may need to bind the socket. */
if(inet_autobind(sk)!=0)
return(-EAGAIN);
return(sk->prot->recvfrom(sk, (unsigned char *) ubuf, size, noblock, flags,
(struct sockaddr_in*)sin, addr_len));
}
static int inet_recv(struct socket *sock, void *ubuf, int size, int noblock,
unsigned flags)
{
/* BSD explicitly states these are the same - so we do it this way to be sure */
return inet_recvfrom(sock,ubuf,size,noblock,flags,NULL,NULL);
}
static int inet_read(struct socket *sock, char *ubuf, int size, int noblock)
{
struct sock *sk = (struct sock *) sock->data;
if(sk->err)
return inet_error(sk);
/* We may need to bind the socket. */
if(inet_autobind(sk))
return(-EAGAIN);
return(sk->prot->read(sk, (unsigned char *) ubuf, size, noblock, 0));
}
static int inet_send(struct socket *sock, void *ubuf, int size, int noblock,
unsigned flags)
{
struct sock *sk = (struct sock *) sock->data;
if (sk->shutdown & SEND_SHUTDOWN)
{
send_sig(SIGPIPE, current, 1);
return(-EPIPE);
}
if(sk->err)
return inet_error(sk);
/* We may need to bind the socket. */
if(inet_autobind(sk)!=0)
return(-EAGAIN);
return(sk->prot->write(sk, (unsigned char *) ubuf, size, noblock, flags));
}
static int inet_write(struct socket *sock, char *ubuf, int size, int noblock)
{
return inet_send(sock,ubuf,size,noblock,0);
}
static int inet_sendto(struct socket *sock, void *ubuf, int size, int noblock,
unsigned flags, struct sockaddr *sin, int addr_len)
{
struct sock *sk = (struct sock *) sock->data;
if (sk->shutdown & SEND_SHUTDOWN)
{
send_sig(SIGPIPE, current, 1);
return(-EPIPE);
}
if (sk->prot->sendto == NULL)
return(-EOPNOTSUPP);
if(sk->err)
return inet_error(sk);
/* We may need to bind the socket. */
if(inet_autobind(sk)!=0)
return -EAGAIN;
return(sk->prot->sendto(sk, (unsigned char *) ubuf, size, noblock, flags,
(struct sockaddr_in *)sin, addr_len));
}
static int inet_shutdown(struct socket *sock, int how)
{
struct sock *sk=(struct sock*)sock->data;
/*
* This should really check to make sure
* the socket is a TCP socket. (WHY AC...)
*/
how++; /* maps 0->1 has the advantage of making bit 1 rcvs and
1->2 bit 2 snds.
2->3 */
if ((how & ~SHUTDOWN_MASK) || how==0) /* MAXINT->0 */
return(-EINVAL);
if (sock->state == SS_CONNECTING && sk->state == TCP_ESTABLISHED)
sock->state = SS_CONNECTED;
if (!tcp_connected(sk->state))
return(-ENOTCONN);
sk->shutdown |= how;
if (sk->prot->shutdown)
sk->prot->shutdown(sk, how);
return(0);
}
static int inet_select(struct socket *sock, int sel_type, select_table *wait )
{
struct sock *sk=(struct sock *) sock->data;
if (sk->prot->select == NULL)
{
return(0);
}
return(sk->prot->select(sk, sel_type, wait));
}
/*
* ioctl() calls you can issue on an INET socket. Most of these are
* device configuration and stuff and very rarely used. Some ioctls
* pass on to the socket itself.
*
* NOTE: I like the idea of a module for the config stuff. ie ifconfig
* loads the devconfigure module does its configuring and unloads it.
* There's a good 20K of config code hanging around the kernel.
*/
static int inet_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
struct sock *sk=(struct sock *)sock->data;
int err, pid;
switch(cmd)
{
case FIOSETOWN:
case SIOCSPGRP:
err=verify_area(VERIFY_READ,(int *)arg,sizeof(long));
if(err)
return err;
pid = get_fs_long((int *) arg);
/* see inet_fcntl */
if (current->pid != pid && current->pgrp != -pid && !suser())
return -EPERM;
sk->proc = pid;
return(0);
case FIOGETOWN:
case SIOCGPGRP:
err=verify_area(VERIFY_WRITE,(void *) arg, sizeof(long));
if(err)
return err;
put_fs_long(sk->proc,(int *)arg);
return(0);
case SIOCGSTAMP:
if(sk->stamp.tv_sec==0)
return -ENOENT;
err=verify_area(VERIFY_WRITE,(void *)arg,sizeof(struct timeval));
if(err)
return err;
memcpy_tofs((void *)arg,&sk->stamp,sizeof(struct timeval));
return 0;
case SIOCADDRT: case SIOCADDRTOLD:
case SIOCDELRT: case SIOCDELRTOLD:
return(ip_rt_ioctl(cmd,(void *) arg));
case SIOCDARP:
case SIOCGARP:
case SIOCSARP:
return(arp_ioctl(cmd,(void *) arg));
#ifdef CONFIG_INET_RARP
case SIOCDRARP:
case SIOCGRARP:
case SIOCSRARP:
return(rarp_ioctl(cmd,(void *) arg));
#endif
case SIOCGIFCONF:
case SIOCGIFFLAGS:
case SIOCSIFFLAGS:
case SIOCGIFADDR:
case SIOCSIFADDR:
/* begin multicast support change */
case SIOCADDMULTI:
case SIOCDELMULTI:
/* end multicast support change */
case SIOCGIFDSTADDR:
case SIOCSIFDSTADDR:
case SIOCGIFBRDADDR:
case SIOCSIFBRDADDR:
case SIOCGIFNETMASK:
case SIOCSIFNETMASK:
case SIOCGIFMETRIC:
case SIOCSIFMETRIC:
case SIOCGIFMEM:
case SIOCSIFMEM:
case SIOCGIFMTU:
case SIOCSIFMTU:
case SIOCSIFLINK:
case SIOCGIFHWADDR:
case SIOCSIFHWADDR:
case OLD_SIOCGIFHWADDR:
case SIOCSIFMAP:
case SIOCGIFMAP:
case SIOCSIFSLAVE:
case SIOCGIFSLAVE:
return(dev_ioctl(cmd,(void *) arg));
default:
if ((cmd >= SIOCDEVPRIVATE) &&
(cmd <= (SIOCDEVPRIVATE + 15)))
return(dev_ioctl(cmd,(void *) arg));
if (sk->prot->ioctl==NULL)
return(-EINVAL);
return(sk->prot->ioctl(sk, cmd, arg));
}
/*NOTREACHED*/
return(0);
}
/*
* This routine must find a socket given a TCP or UDP header.
* Everything is assumed to be in net order.
*
* We give priority to more closely bound ports: if some socket
* is bound to a particular foreign address, it will get the packet
* rather than somebody listening to any address..
*/
struct sock *get_sock(struct proto *prot, unsigned short num,
unsigned long raddr,
unsigned short rnum, unsigned long laddr)
{
struct sock *s;
struct sock *result = NULL;
int badness = -1;
unsigned short hnum;
hnum = ntohs(num);
/*
* SOCK_ARRAY_SIZE must be a power of two. This will work better
* than a prime unless 3 or more sockets end up using the same
* array entry. This should not be a problem because most
* well known sockets don't overlap that much, and for
* the other ones, we can just be careful about picking our
* socket number when we choose an arbitrary one.
*/
for(s = prot->sock_array[hnum & (SOCK_ARRAY_SIZE - 1)];
s != NULL; s = s->next)
{
int score = 0;
if (s->num != hnum)
continue;
if(s->dead && (s->state == TCP_CLOSE))
continue;
/* local address matches? */
if (s->saddr) {
if (s->saddr != laddr)
continue;
score++;
}
/* remote address matches? */
if (s->daddr) {
if (s->daddr != raddr)
continue;
score++;
}
/* remote port matches? */
if (s->dummy_th.dest) {
if (s->dummy_th.dest != rnum)
continue;
score++;
}
/* perfect match? */
if (score == 3)
return s;
/* no, check if this is the best so far.. */
if (score <= badness)
continue;
result = s;
badness = score;
}
return result;
}
/*
* Deliver a datagram to raw sockets.
*/
struct sock *get_sock_raw(struct sock *sk,
unsigned short num,
unsigned long raddr,
unsigned long laddr)
{
struct sock *s;
s=sk;
for(; s != NULL; s = s->next)
{
if (s->num != num)
continue;
if(s->dead && (s->state == TCP_CLOSE))
continue;
if(s->daddr && s->daddr!=raddr)
continue;
if(s->saddr && s->saddr!=laddr)
continue;
return(s);
}
return(NULL);
}
#ifdef CONFIG_IP_MULTICAST
/*
* Deliver a datagram to broadcast/multicast sockets.
*/
struct sock *get_sock_mcast(struct sock *sk,
unsigned short num,
unsigned long raddr,
unsigned short rnum, unsigned long laddr)
{
struct sock *s;
unsigned short hnum;
hnum = ntohs(num);
/*
* SOCK_ARRAY_SIZE must be a power of two. This will work better
* than a prime unless 3 or more sockets end up using the same
* array entry. This should not be a problem because most
* well known sockets don't overlap that much, and for
* the other ones, we can just be careful about picking our
* socket number when we choose an arbitrary one.
*/
s=sk;
for(; s != NULL; s = s->next)
{
if (s->num != hnum)
continue;
if(s->dead && (s->state == TCP_CLOSE))
continue;
if(s->daddr && s->daddr!=raddr)
continue;
if (s->dummy_th.dest != rnum && s->dummy_th.dest != 0)
continue;
if(s->saddr && s->saddr!=laddr)
continue;
return(s);
}
return(NULL);
}
#endif
static struct proto_ops inet_proto_ops = {
AF_INET,
inet_create,
inet_dup,
inet_release,
inet_bind,
inet_connect,
inet_socketpair,
inet_accept,
inet_getname,
inet_read,
inet_write,
inet_select,
inet_ioctl,
inet_listen,
inet_send,
inet_recv,
inet_sendto,
inet_recvfrom,
inet_shutdown,
inet_setsockopt,
inet_getsockopt,
inet_fcntl,
};
extern unsigned long seq_offset;
/*
* Called by socket.c on kernel startup.
*/
void inet_proto_init(struct net_proto *pro)
{
struct inet_protocol *p;
int i;
printk("Swansea University Computer Society TCP/IP for NET3.019/n");
/*
* Tell SOCKET that we are alive...
*/
(void) sock_register(inet_proto_ops.family, &inet_proto_ops);
seq_offset = CURRENT_TIME*250;
/*
* Add all the protocols.
*/
for(i = 0; i < SOCK_ARRAY_SIZE; i++)
{
tcp_prot.sock_array[i] = NULL;
udp_prot.sock_array[i] = NULL;
raw_prot.sock_array[i] = NULL;
}
tcp_prot.inuse = 0;
tcp_prot.highestinuse = 0;
udp_prot.inuse = 0;
udp_prot.highestinuse = 0;
raw_prot.inuse = 0;
raw_prot.highestinuse = 0;
printk("IP Protocols: ");
for(p = inet_protocol_base; p != NULL;)
{
struct inet_protocol *tmp = (struct inet_protocol *) p->next;
inet_add_protocol(p);
printk("%s%s",p->name,tmp?", ":"/n");
p = tmp;
}
/*
* Set the ARP module up
*/
arp_init();
/*
* Set the IP module up
*/
ip_init();
}/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* AF_INET protocol family socket handler.
*
* Version: @(#)af_inet.c (from sock.c) 1.0.17 06/02/93
*
* Authors: Ross Biro, <[email protected]>
* Fred N. van Kempen, <[email protected]>
* Florian La Roche, <[email protected]>
* Alan Cox, <[email protected]>
*
* Changes (see also sock.c)
*
* A.N.Kuznetsov : Socket death error in accept().
* John Richardson : Fix non blocking error in connect()
* so sockets that fail to connect
* don't return -EINPROGRESS.
* Alan Cox : Asynchronous I/O support
* Alan Cox : Keep correct socket pointer on sock structures
* when accept() ed
* Alan Cox : Semantics of SO_LINGER aren't state moved
* to close when you look carefully. With
* this fixed and the accept bug fixed
* some RPC stuff seems happier.
* Niibe Yutaka : 4.4BSD style write async I/O
* Alan Cox,
* Tony Gale : Fixed reuse semantics.
* Alan Cox : bind() shouldn't abort existing but dead
* sockets. Stops FTP netin:.. I hope.
* Alan Cox : bind() works correctly for RAW sockets. Note
* that FreeBSD at least is broken in this respect
* so be careful with compatibility tests...
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#include <linux/config.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <asm/segment.h>
#include <asm/system.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include "ip.h"
#include "protocol.h"
#include "arp.h"
#include "rarp.h"
#include "route.h"
#include "tcp.h"
#include "udp.h"
#include <linux/skbuff.h>
#include "sock.h"
#include "raw.h"
#include "icmp.h"
#define min(a,b) ((a)<(b)?(a):(b))
extern struct proto packet_prot;
/*
* See if a socket number is in use.
*/
//检测端口号，端口使用返回1，否则返回0
static int sk_inuse(struct proto *prot, int num)
{
struct sock *sk;
for(sk = prot->sock_array[num & (SOCK_ARRAY_SIZE -1 )];
sk != NULL; sk=sk->next)
{
if (sk->num == num)
return(1);
}
return(0);
}
/*
* Pick a new socket number
*/
unsigned short get_new_socknum(struct proto *prot, unsigned short base)
{
static int start=0;
/*
* Used to cycle through the port numbers so the
* chances of a confused connection drop.
*/
int i, j;
int best = 0;
int size = 32767; /* a big num. */
struct sock *sk;
if (base == 0)
base = PROT_SOCK+1+(start % 1024);
if (base <= PROT_SOCK)
{
base += PROT_SOCK+(start % 1024);
}
/* Now look through the entire array and try to find an empty ptr. */
for(i=0; i < SOCK_ARRAY_SIZE; i++)
{
j = 0;
sk = prot->sock_array[(i+base+1) &(SOCK_ARRAY_SIZE -1)];
while(sk != NULL)
{
sk = sk->next;
j++;
}
if (j == 0)
{
start =(i+1+start )%1024;
return(i+base+1);
}
if (j < size)
{
best = i;
size = j;
}
}
/* Now make sure the one we want is not in use. */
while(sk_inuse(prot, base +best+1))
{
best += SOCK_ARRAY_SIZE;
}
return(best+base+1);
}
/*
* Add a socket into the socket tables by number.
*/
//加入一个有端口号的sock结构到 sock_array[]中
void put_sock(unsigned short num, struct sock *sk)
{
struct sock *sk1;
struct sock *sk2;
int mask;
unsigned long flags;
sk->num = num;
sk->next = NULL;
num = num &(SOCK_ARRAY_SIZE -1);
/* We can't have an interrupt re-enter here. */
save_flags(flags);
cli();
sk->prot->inuse += 1;
if (sk->prot->highestinuse < sk->prot->inuse)
sk->prot->highestinuse = sk->prot->inuse;
if (sk->prot->sock_array[num] == NULL)
{
sk->prot->sock_array[num] = sk;
restore_flags(flags);
return;
}
restore_flags(flags);
for(mask = 0xff000000; mask != 0xffffffff; mask = (mask >> 8) | mask)
{
if ((mask & sk->saddr) &&
(mask & sk->saddr) != (mask & 0xffffffff))
{
mask = mask << 8;
break;
}
}
cli();
sk1 = sk->prot->sock_array[num];
for(sk2 = sk1; sk2 != NULL; sk2=sk2->next)
{
if (!(sk2->saddr & mask))
{
if (sk2 == sk1)
{
sk->next = sk->prot->sock_array[num];
sk->prot->sock_array[num] = sk;
sti();
return;
}
sk->next = sk2;
sk1->next= sk;
sti();
return;
}
sk1 = sk2;
}
/* Goes at the end. */
sk->next = NULL;
sk1->next = sk;
sti();
}
/*
* Remove a socket from the socket tables.
*/
//删除一个指定的sock结构
static void remove_sock(struct sock *sk1)
{
struct sock *sk2;
unsigned long flags;
if (!sk1->prot)
{
printk("sock.c: remove_sock: sk1->prot == NULL/n");
return;
}
/* We can't have this changing out from under us. */
save_flags(flags);
cli();
sk2 = sk1->prot->sock_array[sk1->num &(SOCK_ARRAY_SIZE -1)];
if (sk2 == sk1)
{
sk1->prot->inuse -= 1;
sk1->prot->sock_array[sk1->num &(SOCK_ARRAY_SIZE -1)] = sk1->next;
restore_flags(flags);
return;
}
while(sk2 && sk2->next != sk1)
{
sk2 = sk2->next;
}
if (sk2)
{
sk1->prot->inuse -= 1;
sk2->next = sk1->next;
restore_flags(flags);
return;
}
restore_flags(flags);
}
/*
* Destroy an AF_INET socket
*/
void destroy_sock(struct sock *sk)
{
struct sk_buff *skb;
sk->inuse = 1; /* just to be safe. */
/* In case it's sleeping somewhere. */
if (!sk->dead)
sk->write_space(sk);
remove_sock(sk);
/* Now we can no longer get new packets. */
delete_timer(sk);
/* Nor send them */
del_timer(&sk->retransmit_timer);
while ((skb = tcp_dequeue_partial(sk)) != NULL) {
IS_SKB(skb);
kfree_skb(skb, FREE_WRITE);
}
/* Cleanup up the write buffer. */
while((skb = skb_dequeue(&sk->write_queue)) != NULL) {
IS_SKB(skb);
kfree_skb(skb, FREE_WRITE);
}
/*
* Don't discard received data until the user side kills its
* half of the socket.
*/
if (sk->dead)
{
while((skb=skb_dequeue(&sk->receive_queue))!=NULL)
{
/*
* This will take care of closing sockets that were
* listening and didn't accept everything.
*/
if (skb->sk != NULL && skb->sk != sk)
{
IS_SKB(skb);
skb->sk->dead = 1;
skb->sk->prot->close(skb->sk, 0);
}
IS_SKB(skb);
kfree_skb(skb, FREE_READ);
}
}
/* Now we need to clean up the send head. */
cli();
for(skb = sk->send_head; skb != NULL; )
{
struct sk_buff *skb2;
/*
* We need to remove skb from the transmit queue,
* or maybe the arp queue.
*/
if (skb->next && skb->prev) {
/* printk("destroy_sock: unlinked skb/n");*/
IS_SKB(skb);
skb_unlink(skb);
}
skb->dev = NULL;
skb2 = skb->link3;
kfree_skb(skb, FREE_WRITE);
skb = skb2;
}
sk->send_head = NULL;
sti();
/* And now the backlog. */
while((skb=skb_dequeue(&sk->back_log))!=NULL)
{
/* this should never happen. */
/* printk("cleaning back_log/n");*/
kfree_skb(skb, FREE_READ);
}
/* Now if it has a half accepted/ closed socket. */
if (sk->pair)
{
sk->pair->dead = 1;
sk->pair->prot->close(sk->pair, 0);
sk->pair = NULL;
}
/*
* Now if everything is gone we can free the socket
* structure, otherwise we need to keep it around until
* everything is gone.
*/
if (sk->dead && sk->rmem_alloc == 0 && sk->wmem_alloc == 0)
{
kfree_s((void *)sk,sizeof(*sk));
}
else
{
/* this should never happen. */
/* actually it can if an ack has just been sent. */
sk->destroy = 1;
sk->ack_backlog = 0;
sk->inuse = 0;
reset_timer(sk, TIME_DESTROY, SOCK_DESTROY_TIME);
}
}
/*
* The routines beyond this point handle the behaviour of an AF_INET
* socket object. Mostly it punts to the subprotocols of IP to do
* the work.
*/
//设置和获取套接字相关信息
static int inet_fcntl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
struct sock *sk;
sk = (struct sock *) sock->data; //void * 可以转换层任何指针类型
switch(cmd)
{
//设置套接字信息
case F_SETOWN:
/*
* This is a little restrictive, but it's the only
* way to make sure that you can't send a sigurg to
* another process.
*/
if (!suser() && current->pgrp != -arg &&
current->pid != arg) return(-EPERM);
sk->proc = arg;
return(0);
//获得套接字信息
case F_GETOWN:
return(sk->proc);
default:
return(-EINVAL);
}
}
/*
* Set socket options on an inet socket.
*/
static int inet_setsockopt(struct socket *sock, int level, int optname,
char *optval, int optlen)
{
struct sock *sk = (struct sock *) sock->data;
if (level == SOL_SOCKET)
return sock_setsockopt(sk,level,optname,optval,optlen);
if (sk->prot->setsockopt==NULL)
return(-EOPNOTSUPP);
else
return sk->prot->setsockopt(sk,level,optname,optval,optlen);
}
/*
* Get a socket option on an AF_INET socket.
*/
static int inet_getsockopt(struct socket *sock, int level, int optname,
char *optval, int *optlen)
{
struct sock *sk = (struct sock *) sock->data;
if (level == SOL_SOCKET)
return sock_getsockopt(sk,level,optname,optval,optlen);
if(sk->prot->getsockopt==NULL)
return(-EOPNOTSUPP);
else
return sk->prot->getsockopt(sk,level,optname,optval,optlen);
}
/*
* Automatically bind an unbound socket.
*/
static int inet_autobind(struct sock *sk)
{
/* We may need to bind the socket. */
if (sk->num == 0)
{ //获得未使用的端口号
sk->num = get_new_socknum(sk->prot, 0);
if (sk->num == 0)
return(-EAGAIN);
//把该sock放入队列中
put_sock(sk->num, sk);
//dummy_th是tcp首部，source是本地端口号，ntohs使用网络字节序
sk->dummy_th.source = ntohs(sk->num);
}
return 0;
}
/*
* Move a socket into listening state.
*/
//对于系统调用到这一层L5就结束了
static int inet_listen(struct socket *sock, int backlog)
{
struct sock *sk = (struct sock *) sock->data;
if(inet_autobind(sk)!=0)
return -EAGAIN;
/* We might as well re use these. */
/*
* note that the backlog is "unsigned char", so truncate it
* somewhere. We might as well truncate it to what everybody
* else does..
*/
if ((unsigned) backlog > 128)
backlog = 128;
sk->max_ack_backlog = backlog;
if (sk->state != TCP_LISTEN)
{
sk->ack_backlog = 0;
sk->state = TCP_LISTEN; //这里是关键
}
return(0);
}
/*
* Default callbacks for user INET sockets. These just wake up
* the user owning the socket.
*/
static void def_callback1(struct sock *sk)
{
if(!sk->dead)
wake_up_interruptible(sk->sleep);
}
static void def_callback2(struct sock *sk,int len)
{
if(!sk->dead)
{
wake_up_interruptible(sk->sleep);
sock_wake_async(sk->socket, 1);
}
}
static void def_callback3(struct sock *sk)
{
if(!sk->dead)
{
wake_up_interruptible(sk->sleep);
sock_wake_async(sk->socket, 2);
}
}
/*
* Create an inet socket.
*
* FIXME: Gcc would generate much better code if we set the parameters
* up in in-memory structure order. Gcc68K even more so
*/
//inet 层sock结构的创建和初始化
static int inet_create(struct socket *sock, int protocol)
{
struct sock *sk;
struct proto *prot;
int err;
//分析sock结构
sk = (struct sock *) kmalloc(sizeof(*sk), GFP_KERNEL);
if (sk == NULL)
return(-ENOBUFS);
sk->num = 0;
sk->reuse = 0;
switch(sock->type)
{
//流式套接字
case SOCK_STREAM:
case SOCK_SEQPACKET:
//在socket系统调用时,我们一般将protocol参数设置为0，如果设置为
//非0的话，对于不同类型必须正确值
if (protocol && protocol != IPPROTO_TCP)
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPROTONOSUPPORT);
}
protocol = IPPROTO_TCP;
//TCP_NO_CHECK定义为1，表示默认使用校验，这里不用
sk->no_check = TCP_NO_CHECK;
//prot变量初始化为tcp_proc，
prot = &tcp_prot;
break;
//报文套接字，则使用UDP协议操作集
case SOCK_DGRAM:
if (protocol && protocol != IPPROTO_UDP)
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPROTONOSUPPORT);
}
protocol = IPPROTO_UDP;
sk->no_check = UDP_NO_CHECK;
prot=&udp_prot;
break;
//原始套接字类型，主持此时protocol参数表示端口号
case SOCK_RAW:
if (!suser())
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPERM);
}
if (!protocol)
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPROTONOSUPPORT);
}
prot = &raw_prot;
sk->reuse = 1;
sk->no_check = 0; /*
* Doesn't matter no checksum is
* performed anyway.
*/
sk->num = protocol;
break;
//包套接字，该套接字在网络层直接进行数据包的收发
case SOCK_PACKET:
if (!suser())
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPERM);
}
if (!protocol)
{
kfree_s((void *)sk, sizeof(*sk));
return(-EPROTONOSUPPORT);
}
prot = &packet_prot;
sk->reuse = 1;
sk->no_check = 0; /* Doesn't matter no checksum is
* performed anyway.
*/
sk->num = protocol;
break;
default:
kfree_s((void *)sk, sizeof(*sk));
return(-ESOCKTNOSUPPORT);
}
sk->socket = sock;
#ifdef CONFIG_TCP_NAGLE_OFF
sk->nonagle = 1;
#else
sk->nonagle = 0;
#endif
sk->type = sock->type;
sk->stamp.tv_sec=0;
sk->protocol = protocol;
sk->wmem_alloc = 0;
sk->rmem_alloc = 0;
sk->sndbuf = SK_WMEM_MAX;
sk->rcvbuf = SK_RMEM_MAX;
sk->pair = NULL;
sk->opt = NULL;
sk->write_seq = 0;
sk->acked_seq = 0;
sk->copied_seq = 0;
sk->fin_seq = 0;
sk->urg_seq = 0;
sk->urg_data = 0;
sk->proc = 0;
sk->rtt = 0; /*TCP_WRITE_TIME << 3;*/
sk->rto = TCP_TIMEOUT_INIT; /*TCP_WRITE_TIME*/
sk->mdev = 0;
sk->backoff = 0;
sk->packets_out = 0;
sk->cong_window = 1; /* start with only sending one packet at a time. */
sk->cong_count = 0;
sk->ssthresh = 0;
sk->max_window = 0;
sk->urginline = 0;
sk->intr = 0;
sk->linger = 0;
sk->destroy = 0;
sk->priority = 1;
sk->shutdown = 0;
sk->keepopen = 0;
sk->zapped = 0;
sk->done = 0;
sk->ack_backlog = 0;
sk->window = 0;
sk->bytes_rcv = 0;
sk->state = TCP_CLOSE;
sk->dead = 0;
sk->ack_timed = 0;
sk->partial = NULL;
sk->user_mss = 0;
sk->debug = 0;
/* this is how many unacked bytes we will accept for this socket. */
sk->max_unacked = 2048; /* needs to be at most 2 full packets. */
/* how many packets we should send before forcing an ack.
if this is set to zero it is the same as sk->delay_acks = 0 */
sk->max_ack_backlog = 0;
sk->inuse = 0;
sk->delay_acks = 0;
skb_queue_head_init(&sk->write_queue);
skb_queue_head_init(&sk->receive_queue);
sk->mtu = 576;
sk->prot = prot;
sk->sleep = sock->wait;
sk->daddr = 0;
sk->saddr = 0 /* ip_my_addr() */;
sk->err = 0;
sk->next = NULL;
sk->pair = NULL;
sk->send_tail = NULL;
sk->send_head = NULL;
sk->timeout = 0;
sk->broadcast = 0;
sk->localroute = 0;
init_timer(&sk->timer);
init_timer(&sk->retransmit_timer);
sk->timer.data = (unsigned long)sk;
sk->timer.function = &net_timer;
skb_queue_head_init(&sk->back_log);
sk->blog = 0;
sock->data =(void *) sk;
sk->dummy_th.doff = sizeof(sk->dummy_th)/4;
sk->dummy_th.res1=0;
sk->dummy_th.res2=0;
sk->dummy_th.urg_ptr = 0;
sk->dummy_th.fin = 0;
sk->dummy_th.syn = 0;
sk->dummy_th.rst = 0;
sk->dummy_th.psh = 0;
sk->dummy_th.ack = 0;
sk->dummy_th.urg = 0;
sk->dummy_th.dest = 0;
sk->ip_tos=0;
sk->ip_ttl=64;
#ifdef CONFIG_IP_MULTICAST
sk->ip_mc_loop=1;
sk->ip_mc_ttl=1;
*sk->ip_mc_name=0;
sk->ip_mc_list=NULL;
#endif
sk->state_change = def_callback1;
sk->data_ready = def_callback2;
sk->write_space = def_callback3;
sk->error_report = def_callback1;
if (sk->num)
{
/*
* It assumes that any protocol which allows
* the user to assign a number at socket
* creation time automatically
* shares.
*/
put_sock(sk->num, sk);
sk->dummy_th.source = ntohs(sk->num);
}
if (sk->prot->init)
{
err = sk->prot->init(sk);
if (err != 0)
{
destroy_sock(sk);
return(err);
}
}
return(0);
}
/*
* Duplicate a socket.
*/
static int inet_dup(struct socket *newsock, struct socket *oldsock)
{
return(inet_create(newsock,((struct sock *)(oldsock->data))->protocol));
}
/*
* Return 1 if we still have things to send in our buffers.
*/
static inline int closing(struct sock * sk)
{
switch (sk->state) {
case TCP_FIN_WAIT1:
case TCP_CLOSING:
case TCP_LAST_ACK:
return 1;
}
return 0;
}
/*
* The peer socket should always be NULL (or else). When we call this
* function we are destroying the object and from then on nobody
* should refer to it.
*/
static int inet_release(struct socket *sock, struct socket *peer)
{
struct sock *sk = (struct sock *) sock->data;
if (sk == NULL)
return(0);
sk->state_change(sk);
/* Start closing the connection. This may take a while. */
#ifdef CONFIG_IP_MULTICAST
/* Applications forget to leave groups before exiting */
ip_mc_drop_socket(sk);
#endif
/*
* If linger is set, we don't return until the close
* is complete. Other wise we return immediately. The
* actually closing is done the same either way.
*
* If the close is due to the process exiting, we never
* linger..
*/
if (sk->linger == 0 || (current->flags & PF_EXITING))
{
sk->prot->close(sk,0);
sk->dead = 1;
}
else
{
sk->prot->close(sk, 0);
cli();
if (sk->lingertime)
current->timeout = jiffies + HZ*sk->lingertime;
while(closing(sk) && current->timeout>0)
{
interruptible_sleep_on(sk->sleep);
if (current->signal & ~current->blocked)
{
break;
#if 0
/* not working now - closes can't be restarted */
sti();
current->timeout=0;
return(-ERESTARTSYS);
#endif
}
}
current->timeout=0;
sti();
sk->dead = 1;
}
sk->inuse = 1;
/* This will destroy it. */
sock->data = NULL;
release_sock(sk);
sk->socket = NULL;
return(0);
}
/* this needs to be changed to disallow
the rebinding of sockets. What error
should it return? */
//bind系统调用在INET层实现
static int inet_bind(struct socket *sock, struct sockaddr *uaddr,
int addr_len)
{
struct sockaddr_in *addr=(struct sockaddr_in *)uaddr;
struct sock *sk=(struct sock *)sock->data, *sk2;
unsigned short snum = 0 /* Stoopid compiler.. this IS ok */;
int chk_addr_ret;
//检测状态，绑定时，该套接字应出于关闭状态
/* check this error. */
if (sk->state != TCP_CLOSE)
return(-EIO);
if(addr_len<sizeof(struct sockaddr_in))
return -EINVAL;
//对于非原始套接字套接字类型，绑定地址前没有端口号
if(sock->type != SOCK_RAW)
{
if (sk->num != 0)
return(-EINVAL);
snum = ntohs(addr->sin_port);
/*
* We can't just leave the socket bound wherever it is, it might
* be bound to a privileged port. However, since there seems to
* be a bug here, we will leave it if the port is not privileged.
*/
if (snum == 0)
{ //分配一个端口号
snum = get_new_socknum(sk->prot, 0);
}
if (snum < PROT_SOCK && !suser())
return(-EACCES);
}
chk_addr_ret = ip_chk_addr(addr->sin_addr.s_addr); //检查是否是一个本地地址
if (addr->sin_addr.s_addr != 0 && chk_addr_ret != IS_MYADDR && chk_addr_ret != IS_MULTICAST)
return(-EADDRNOTAVAIL); /* Source address MUST be ours! */
if (chk_addr_ret || addr->sin_addr.s_addr == 0)
sk->saddr = addr->sin_addr.s_addr; //没有地址自动分配
if(sock->type != SOCK_RAW)
{
/* Make sure we are allowed to bind here. */
cli();
for(sk2 = sk->prot->sock_array[snum & (SOCK_ARRAY_SIZE -1)];
sk2 != NULL; sk2 = sk2->next)
{
/* should be below! */
if (sk2->num != snum)
continue;
if (!sk->reuse)
{
sti();
return(-EADDRINUSE);
}
if (sk2->num != snum)
continue; /* more than one */
if (sk2->saddr != sk->saddr)
continue; /* socket per slot ! -FB */
if (!sk2->reuse || sk2->state==TCP_LISTEN)
{
sti();
return(-EADDRINUSE);
}
}
sti();
remove_sock(sk);
put_sock(snum, sk);
//初始化本地端口，ip地址
sk->dummy_th.source = ntohs(sk->num);
sk->daddr = 0;
sk->dummy_th.dest = 0;
}
return(0);
}
/*
* Handle sk->err properly. The cli/sti matter.
*/
static int inet_error(struct sock *sk)
{
unsigned long flags;
int err;
save_flags(flags);
cli();
err=sk->err;
sk->err=0;
restore_flags(flags);
return -err;
}
/*
* Connect to a remote host. There is regrettably still a little
* TCP 'magic' in here.
*/
//tcp3次握手
static int inet_connect(struct socket *sock, struct sockaddr * uaddr,
int addr_len, int flags)
{
struct sock *sk=(struct sock *)sock->data;
int err;
sock->conn = NULL;
if (sock->state == SS_CONNECTING && tcp_connected(sk->state))
{
sock->state = SS_CONNECTED;
/* Connection completing after a connect/EINPROGRESS/select/connect */
return 0; /* Rock and roll */
}
if (sock->state == SS_CONNECTING && sk->protocol == IPPROTO_TCP && (flags & O_NONBLOCK)) {
if (sk->err != 0)
{
err=sk->err;
sk->err=0;
return -err;
}
return -EALREADY; /* Connecting is currently in progress */
}
if (sock->state != SS_CONNECTING)
{
/* We may need to bind the socket. */
if(inet_autobind(sk)!=0)
return(-EAGAIN);
if (sk->prot->connect == NULL)
return(-EOPNOTSUPP);
err = sk->prot->connect(sk, (struct sockaddr_in *)uaddr, addr_len);
if (err < 0)
return(err);
sock->state = SS_CONNECTING;
}
if (sk->state > TCP_FIN_WAIT2 && sock->state==SS_CONNECTING)
{
sock->state=SS_UNCONNECTED;
cli();
err=sk->err;
sk->err=0;
sti();
return -err;
}
if (sk->state != TCP_ESTABLISHED &&(flags & O_NONBLOCK))
return(-EINPROGRESS);
cli(); /* avoid the race condition */
while(sk->state == TCP_SYN_SENT || sk->state == TCP_SYN_RECV)
{
interruptible_sleep_on(sk->sleep);
if (current->signal & ~current->blocked)
{
sti();
return(-ERESTARTSYS);
}
/* This fixes a nasty in the tcp/ip code. There is a hideous hassle with
icmp error packets wanting to close a tcp or udp socket. */
if(sk->err && sk->protocol == IPPROTO_TCP)
{
sti();
sock->state = SS_UNCONNECTED;
err = -sk->err;
sk->err=0;
return err; /* set by tcp_err() */
}
}
sti();
sock->state = SS_CONNECTED;
if (sk->state != TCP_ESTABLISHED && sk->err)
{
sock->state = SS_UNCONNECTED;
err=sk->err;
sk->err=0;
return(-err);
}
return(0);
}
static int inet_socketpair(struct socket *sock1, struct socket *sock2)
{
return(-EOPNOTSUPP);
}
/*
* Accept a pending connection. The TCP layer now gives BSD semantics.
*/
static int inet_accept(struct socket *sock, struct socket *newsock, int flags)
{
struct sock *sk1, *sk2;
int err;
sk1 = (struct sock *) sock->data;
/*
* We've been passed an extra socket.
* We need to free it up because the tcp module creates
* its own when it accepts one.
*/
if (newsock->data)
{
struct sock *sk=(struct sock *)newsock->data;
newsock->data=NULL;
sk->dead = 1;
destroy_sock(sk);
}
if (sk1->prot->accept == NULL)
return(-EOPNOTSUPP);
/* Restore the state if we have been interrupted, and then returned. */
if (sk1->pair != NULL )
{
sk2 = sk1->pair;
sk1->pair = NULL;
}
else
{
sk2 = sk1->prot->accept(sk1,flags);
if (sk2 == NULL)
{
if (sk1->err <= 0)
printk("Warning sock.c:sk1->err <= 0. Returning non-error./n");
err=sk1->err;
sk1->err=0;
return(-err);
}
}
newsock->data = (void *)sk2;
sk2->sleep = newsock->wait;
sk2->socket = newsock;
newsock->conn = NULL;
if (flags & O_NONBLOCK)
return(0);
cli(); /* avoid the race. */
while(sk2->state == TCP_SYN_RECV)
{
interruptible_sleep_on(sk2->sleep);
if (current->signal & ~current->blocked)
{
sti();
sk1->pair = sk2;
sk2->sleep = NULL;
sk2->socket=NULL;
newsock->data = NULL;
return(-ERESTARTSYS);
}
}
sti();
if (sk2->state != TCP_ESTABLISHED && sk2->err > 0)
{
err = -sk2->err;
sk2->err=0;
sk2->dead=1; /* ANK */
destroy_sock(sk2);
newsock->data = NULL;
return(err);
}
newsock->state = SS_CONNECTED;
return(0);
}
/*
* This does both peername and sockname.
*/
static int inet_getname(struct socket *sock, struct sockaddr *uaddr,
int *uaddr_len, int peer)
{
struct sockaddr_in *sin=(struct sockaddr_in *)uaddr;
struct sock *sk;
sin->sin_family = AF_INET;
sk = (struct sock *) sock->data;
if (peer)
{
if (!tcp_connected(sk->state))
return(-ENOTCONN);
sin->sin_port = sk->dummy_th.dest;
sin->sin_addr.s_addr = sk->daddr;
}
else
{
sin->sin_port = sk->dummy_th.source;
if (sk->saddr == 0)
sin->sin_addr.s_addr = ip_my_addr();
else
sin->sin_addr.s_addr = sk->saddr;
}
*uaddr_len = sizeof(*sin);
return(0);
}
/*
* The assorted BSD I/O operations
*/
static int inet_recvfrom(struct socket *sock, void *ubuf, int size, int noblock,
unsigned flags, struct sockaddr *sin, int *addr_len )
{
struct sock *sk = (struct sock *) sock->data;
if (sk->prot->recvfrom == NULL)
return(-EOPNOTSUPP);
if(sk->err)
return inet_error(sk);
/* We may need to bind the socket. */
if(inet_autobind(sk)!=0)
return(-EAGAIN);
return(sk->prot->recvfrom(sk, (unsigned char *) ubuf, size, noblock, flags,
(struct sockaddr_in*)sin, addr_len));
}
static int inet_recv(struct socket *sock, void *ubuf, int size, int noblock,
unsigned flags)
{
/* BSD explicitly states these are the same - so we do it this way to be sure */
return inet_recvfrom(sock,ubuf,size,noblock,flags,NULL,NULL);
}
static int inet_read(struct socket *sock, char *ubuf, int size, int noblock)
{
struct sock *sk = (struct sock *) sock->data;
if(sk->err)
return inet_error(sk);
/* We may need to bind the socket. */
if(inet_autobind(sk))
return(-EAGAIN);
return(sk->prot->read(sk, (unsigned char *) ubuf, size, noblock, 0));
}
static int inet_send(struct socket *sock, void *ubuf, int size, int noblock,
unsigned flags)
{
struct sock *sk = (struct sock *) sock->data;
if (sk->shutdown & SEND_SHUTDOWN)
{
send_sig(SIGPIPE, current, 1);
return(-EPIPE);
}
if(sk->err)
return inet_error(sk);
/* We may need to bind the socket. */
if(inet_autobind(sk)!=0)
return(-EAGAIN);
return(sk->prot->write(sk, (unsigned char *) ubuf, size, noblock, flags));
}
static int inet_write(struct socket *sock, char *ubuf, int size, int noblock)
{
return inet_send(sock,ubuf,size,noblock,0);
}
static int inet_sendto(struct socket *sock, void *ubuf, int size, int noblock,
unsigned flags, struct sockaddr *sin, int addr_len)
{
struct sock *sk = (struct sock *) sock->data;
if (sk->shutdown & SEND_SHUTDOWN)
{
send_sig(SIGPIPE, current, 1);
return(-EPIPE);
}
if (sk->prot->sendto == NULL)
return(-EOPNOTSUPP);
if(sk->err)
return inet_error(sk);
/* We may need to bind the socket. */
if(inet_autobind(sk)!=0)
return -EAGAIN;
return(sk->prot->sendto(sk, (unsigned char *) ubuf, size, noblock, flags,
(struct sockaddr_in *)sin, addr_len));
}
static int inet_shutdown(struct socket *sock, int how)
{
struct sock *sk=(struct sock*)sock->data;
/*
* This should really check to make sure
* the socket is a TCP socket. (WHY AC...)
*/
how++; /* maps 0->1 has the advantage of making bit 1 rcvs and
1->2 bit 2 snds.
2->3 */
if ((how & ~SHUTDOWN_MASK) || how==0) /* MAXINT->0 */
return(-EINVAL);
if (sock->state == SS_CONNECTING && sk->state == TCP_ESTABLISHED)
sock->state = SS_CONNECTED;
if (!tcp_connected(sk->state))
return(-ENOTCONN);
sk->shutdown |= how;
if (sk->prot->shutdown)
sk->prot->shutdown(sk, how);
return(0);
}
static int inet_select(struct socket *sock, int sel_type, select_table *wait )
{
struct sock *sk=(struct sock *) sock->data;
if (sk->prot->select == NULL)
{
return(0);
}
return(sk->prot->select(sk, sel_type, wait));
}
/*
* ioctl() calls you can issue on an INET socket. Most of these are
* device configuration and stuff and very rarely used. Some ioctls
* pass on to the socket itself.
*
* NOTE: I like the idea of a module for the config stuff. ie ifconfig
* loads the devconfigure module does its configuring and unloads it.
* There's a good 20K of config code hanging around the kernel.
*/
static int inet_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
struct sock *sk=(struct sock *)sock->data;
int err, pid;
switch(cmd)
{
case FIOSETOWN:
case SIOCSPGRP:
err=verify_area(VERIFY_READ,(int *)arg,sizeof(long));
if(err)
return err;
pid = get_fs_long((int *) arg);
/* see inet_fcntl */
if (current->pid != pid && current->pgrp != -pid && !suser())
return -EPERM;
sk->proc = pid;
return(0);
case FIOGETOWN:
case SIOCGPGRP:
err=verify_area(VERIFY_WRITE,(void *) arg, sizeof(long));
if(err)
return err;
put_fs_long(sk->proc,(int *)arg);
return(0);
case SIOCGSTAMP:
if(sk->stamp.tv_sec==0)
return -ENOENT;
err=verify_area(VERIFY_WRITE,(void *)arg,sizeof(struct timeval));
if(err)
return err;
memcpy_tofs((void *)arg,&sk->stamp,sizeof(struct timeval));
return 0;
case SIOCADDRT: case SIOCADDRTOLD:
case SIOCDELRT: case SIOCDELRTOLD:
return(ip_rt_ioctl(cmd,(void *) arg));
case SIOCDARP:
case SIOCGARP:
case SIOCSARP:
return(arp_ioctl(cmd,(void *) arg));
#ifdef CONFIG_INET_RARP
case SIOCDRARP:
case SIOCGRARP:
case SIOCSRARP:
return(rarp_ioctl(cmd,(void *) arg));
#endif
case SIOCGIFCONF:
case SIOCGIFFLAGS:
case SIOCSIFFLAGS:
case SIOCGIFADDR:
case SIOCSIFADDR:
/* begin multicast support change */
case SIOCADDMULTI:
case SIOCDELMULTI:
/* end multicast support change */
case SIOCGIFDSTADDR:
case SIOCSIFDSTADDR:
case SIOCGIFBRDADDR:
case SIOCSIFBRDADDR:
case SIOCGIFNETMASK:
case SIOCSIFNETMASK:
case SIOCGIFMETRIC:
case SIOCSIFMETRIC:
case SIOCGIFMEM:
case SIOCSIFMEM:
case SIOCGIFMTU:
case SIOCSIFMTU:
case SIOCSIFLINK:
case SIOCGIFHWADDR:
case SIOCSIFHWADDR:
case OLD_SIOCGIFHWADDR:
case SIOCSIFMAP:
case SIOCGIFMAP:
case SIOCSIFSLAVE:
case SIOCGIFSLAVE:
return(dev_ioctl(cmd,(void *) arg));
default:
if ((cmd >= SIOCDEVPRIVATE) &&
(cmd <= (SIOCDEVPRIVATE + 15)))
return(dev_ioctl(cmd,(void *) arg));
if (sk->prot->ioctl==NULL)
return(-EINVAL);
return(sk->prot->ioctl(sk, cmd, arg));
}
/*NOTREACHED*/
return(0);
}
/*
* This routine must find a socket given a TCP or UDP header.
* Everything is assumed to be in net order.
*
* We give priority to more closely bound ports: if some socket
* is bound to a particular foreign address, it will get the packet
* rather than somebody listening to any address..
*/
struct sock *get_sock(struct proto *prot, unsigned short num,
unsigned long raddr,
unsigned short rnum, unsigned long laddr)
{
struct sock *s;
struct sock *result = NULL;
int badness = -1;
unsigned short hnum;
hnum = ntohs(num);
/*
* SOCK_ARRAY_SIZE must be a power of two. This will work better
* than a prime unless 3 or more sockets end up using the same
* array entry. This should not be a problem because most
* well known sockets don't overlap that much, and for
* the other ones, we can just be careful about picking our
* socket number when we choose an arbitrary one.
*/
for(s = prot->sock_array[hnum & (SOCK_ARRAY_SIZE - 1)];
s != NULL; s = s->next)
{
int score = 0;
if (s->num != hnum)
continue;
if(s->dead && (s->state == TCP_CLOSE))
continue;
/* local address matches? */
if (s->saddr) {
if (s->saddr != laddr)
continue;
score++;
}
/* remote address matches? */
if (s->daddr) {
if (s->daddr != raddr)
continue;
score++;
}
/* remote port matches? */
if (s->dummy_th.dest) {
if (s->dummy_th.dest != rnum)
continue;
score++;
}
/* perfect match? */
if (score == 3)
return s;
/* no, check if this is the best so far.. */
if (score <= badness)
continue;
result = s;
badness = score;
}
return result;
}
/*
* Deliver a datagram to raw sockets.
*/
struct sock *get_sock_raw(struct sock *sk,
unsigned short num,
unsigned long raddr,
unsigned long laddr)
{
struct sock *s;
s=sk;
for(; s != NULL; s = s->next)
{
if (s->num != num)
continue;
if(s->dead && (s->state == TCP_CLOSE))
continue;
if(s->daddr && s->daddr!=raddr)
continue;
if(s->saddr && s->saddr!=laddr)
continue;
return(s);
}
return(NULL);
}
#ifdef CONFIG_IP_MULTICAST
/*
* Deliver a datagram to broadcast/multicast sockets.
*/
struct sock *get_sock_mcast(struct sock *sk,
unsigned short num,
unsigned long raddr,
unsigned short rnum, unsigned long laddr)
{
struct sock *s;
unsigned short hnum;
hnum = ntohs(num);
/*
* SOCK_ARRAY_SIZE must be a power of two. This will work better
* than a prime unless 3 or more sockets end up using the same
* array entry. This should not be a problem because most
* well known sockets don't overlap that much, and for
* the other ones, we can just be careful about picking our
* socket number when we choose an arbitrary one.
*/
s=sk;
for(; s != NULL; s = s->next)
{
if (s->num != hnum)
continue;
if(s->dead && (s->state == TCP_CLOSE))
continue;
if(s->daddr && s->daddr!=raddr)
continue;
if (s->dummy_th.dest != rnum && s->dummy_th.dest != 0)
continue;
if(s->saddr && s->saddr!=laddr)
continue;
return(s);
}
return(NULL);
}
#endif
//INET操作集的定义
static struct proto_ops inet_proto_ops = {
AF_INET,
inet_create,
inet_dup,
inet_release,
inet_bind,
inet_connect,
inet_socketpair,
inet_accept,
inet_getname,
inet_read,
inet_write,
inet_select,
inet_ioctl,
inet_listen,
inet_send,
inet_recv,
inet_sendto,
inet_recvfrom,
inet_shutdown,
inet_setsockopt,
inet_getsockopt,
inet_fcntl,
};
extern unsigned long seq_offset;
/*
* Called by socket.c on kernel startup.
*/
//INET域协议的初始化，
void inet_proto_init(struct net_proto *pro)
{
struct inet_protocol *p;
int i;
printk("Swansea University Computer Society TCP/IP for NET3.019/n");
/*
* Tell SOCKET that we are alive...
*/
(void) sock_register(inet_proto_ops.family, &inet_proto_ops);
seq_offset = CURRENT_TIME*250;
/*
* Add all the protocols.
*/
for(i = 0; i < SOCK_ARRAY_SIZE; i++)
{
tcp_prot.sock_array[i] = NULL;
udp_prot.sock_array[i] = NULL;
raw_prot.sock_array[i] = NULL;
}
tcp_prot.inuse = 0;
tcp_prot.highestinuse = 0;
udp_prot.inuse = 0;
udp_prot.highestinuse = 0;
raw_prot.inuse = 0;
raw_prot.highestinuse = 0;
printk("IP Protocols: ");
for(p = inet_protocol_base; p != NULL;)
{
struct inet_protocol *tmp = (struct inet_protocol *) p->next;
inet_add_protocol(p);
printk("%s%s",p->name,tmp?", ":"/n");
p = tmp;
}
/*
* Set the ARP module up
*/
arp_init();
/*
* Set the IP module up
*/
ip_init();
}
小结：
af_inet.c 文件作为INET层处理来自BSD层的请求，并完成相应工作后继续请求发给下层的传输层进行处理，这种分层具有很好的扩展性，层次分明，便于管理。
下次我们来继续分析传输层代码。