LINUX协议栈详解 协议处理
协议处理，主要介绍了从驱动中获取数据后，如何进行分发给不同的协议处理，包括IP协议、ARP协议等处理。
__netif_receive_skb协议处理的开始，主要的数据结构是ptype_all和ptype_base，其中ptype_all是一个链表结构，ptype_base则是一个数组，并通过hash来type来实现索引。
list_for_each_entry_rcu(ptype, &ptype_all, list) {
if (!ptype->dev || ptype->dev == skb->dev) {
if (pt_prev)
ret = deliver_skb(skb, pt_prev, orig_dev);
pt_prev = ptype;
}
}type = skb->protocol;
list_for_each_entry_rcu(ptype,
&ptype_base[ntohs(type) & PTYPE_HASH_MASK], list) {
if (ptype->type == type &&
(ptype->dev == null_or_dev || ptype->dev == skb->dev ||
ptype->dev == orig_dev)) {
if (pt_prev)
ret = deliver_skb(skb, pt_prev, orig_dev);
pt_prev = ptype;
}
}现在有几个问题，
1，什么时候注册的？
注册是通过dev_add_pack来实现的，
IP协议
static struct packet_type ip_packet_type __read_mostly = {
.type = cpu_to_be16(ETH_P_IP),
.func = ip_rcv,
.gso_send_check = inet_gso_send_check,
.gso_segment = inet_gso_segment,
.gro_receive = inet_gro_receive,
.gro_complete = inet_gro_complete,
};在inet_init调用dev_add_pack来注册。
ARP协议
static struct packet_type arp_packet_type __read_mostly = {
.type = cpu_to_be16(ETH_P_ARP),
.func = arp_rcv,
};所有处理的协议号
/*
* These are the defined Ethernet Protocol ID's.
*/
#define ETH_P_LOOP 0x0060 /* Ethernet Loopback packet */
#define ETH_P_PUP 0x0200 /* Xerox PUP packet */
#define ETH_P_PUPAT 0x0201 /* Xerox PUP Addr Trans packet */
#define ETH_P_IP 0x0800 /* Internet Protocol packet */
#define ETH_P_X25 0x0805 /* CCITT X.25 */
#define ETH_P_ARP 0x0806 /* Address Resolution packet */
#define ETH_P_BPQ 0x08FF /* G8BPQ AX.25 Ethernet Packet [ NOT AN OFFICIALLY REGISTERED ID ] */
#define ETH_P_IEEEPUP 0x0a00 /* Xerox IEEE802.3 PUP packet */
#define ETH_P_IEEEPUPAT 0x0a01 /* Xerox IEEE802.3 PUP Addr Trans packet */
#define ETH_P_DEC 0x6000 /* DEC Assigned proto */
#define ETH_P_DNA_DL 0x6001 /* DEC DNA Dump/Load */
#define ETH_P_DNA_RC 0x6002 /* DEC DNA Remote Console */
#define ETH_P_DNA_RT 0x6003 /* DEC DNA Routing */
#define ETH_P_LAT 0x6004 /* DEC LAT */
#define ETH_P_DIAG 0x6005 /* DEC Diagnostics */
#define ETH_P_CUST 0x6006 /* DEC Customer use */
#define ETH_P_SCA 0x6007 /* DEC Systems Comms Arch */
#define ETH_P_TEB 0x6558 /* Trans Ether Bridging */
#define ETH_P_RARP 0x8035 /* Reverse Addr Res packet */
#define ETH_P_ATALK 0x809B /* Appletalk DDP */
#define ETH_P_AARP 0x80F3 /* Appletalk AARP */
#define ETH_P_8021Q 0x8100 /* 802.1Q VLAN Extended Header */
#define ETH_P_IPX 0x8137 /* IPX over DIX */
#define ETH_P_IPV6 0x86DD /* IPv6 over bluebook */
#define ETH_P_PAUSE 0x8808 /* IEEE Pause frames. See 802.3 31B */
#define ETH_P_SLOW 0x8809 /* Slow Protocol. See 802.3ad 43B */
#define ETH_P_WCCP 0x883E /* Web-cache coordination protocol
* defined in draft-wilson-wrec-wccp-v2-00.txt */
#define ETH_P_PPP_DISC 0x8863 /* PPPoE discovery messages */
#define ETH_P_PPP_SES 0x8864 /* PPPoE session messages */
#define ETH_P_MPLS_UC 0x8847 /* MPLS Unicast traffic */
#define ETH_P_MPLS_MC 0x8848 /* MPLS Multicast traffic */
#define ETH_P_ATMMPOA 0x884c /* MultiProtocol Over ATM */
#define ETH_P_LINK_CTL 0x886c /* HPNA, wlan link local tunnel */
#define ETH_P_ATMFATE 0x8884 /* Frame-based ATM Transport
* over Ethernet
*/
#define ETH_P_PAE 0x888E /* Port Access Entity (IEEE 802.1X) */
#define ETH_P_AOE 0x88A2 /* ATA over Ethernet */
#define ETH_P_TIPC 0x88CA /* TIPC */
#define ETH_P_1588 0x88F7 /* IEEE 1588 Timesync */
#define ETH_P_FCOE 0x8906 /* Fibre Channel over Ethernet */
#define ETH_P_FIP 0x8914 /* FCoE Initialization Protocol */
#define ETH_P_EDSA 0xDADA /* Ethertype DSA [ NOT AN OFFICIALLY REGISTERED ID ] */
/*
* Non DIX types. Won't clash for 1500 types.
*/
#define ETH_P_802_3 0x0001 /* Dummy type for 802.3 frames */
#define ETH_P_AX25 0x0002 /* Dummy protocol id for AX.25 */
#define ETH_P_ALL 0x0003 /* Every packet (be careful!!!) */
#define ETH_P_802_2 0x0004 /* 802.2 frames */
#define ETH_P_SNAP 0x0005 /* Internal only */
#define ETH_P_DDCMP 0x0006 /* DEC DDCMP: Internal only */
#define ETH_P_WAN_PPP 0x0007 /* Dummy type for WAN PPP frames*/
#define ETH_P_PPP_MP 0x0008 /* Dummy type for PPP MP frames */
#define ETH_P_LOCALTALK 0x0009 /* Localtalk pseudo type */
#define ETH_P_CAN 0x000C /* Controller Area Network */
#define ETH_P_PPPTALK 0x0010 /* Dummy type for Atalk over PPP*/
#define ETH_P_TR_802_2 0x0011 /* 802.2 frames */
#define ETH_P_MOBITEX 0x0015 /* Mobitex ([email protected]) */
#define ETH_P_CONTROL 0x0016 /* Card specific control frames */
#define ETH_P_IRDA 0x0017 /* Linux-IrDA */
#define ETH_P_ECONET 0x0018 /* Acorn Econet */
#define ETH_P_HDLC 0x0019 /* HDLC frames */
#define ETH_P_ARCNET 0x001A /* 1A for ArcNet :-) */
#define ETH_P_DSA 0x001B /* Distributed Switch Arch. */
#define ETH_P_TRAILER 0x001C /* Trailer switch tagging */
#define ETH_P_PHONET 0x00F5 /* Nokia Phonet frames */
#define ETH_P_IEEE802154 0x00F6 /* IEEE802.15.4 frame */
#define ETH_P_CAIF 0x00F7 /* ST-Ericsson CAIF protocol */2，什么时候赋值 skb->protocol
由驱动负责给protocol赋值，且通过eth_type_trans赋值，同时skb->pkt_type也是在这个函数中赋值的。
/* Packet types */
#define PACKET_HOST 0 /* To us */
#define PACKET_BROADCAST 1 /* To all */
#define PACKET_MULTICAST 2 /* To group */
#define PACKET_OTHERHOST 3 /* To someone else */
#define PACKET_OUTGOING 4 /* Outgoing of any type */到现在我们知道了协议处理过程，也就很自然的进入了具体协议等研究，例如ARP的处理，IP数据包的处理等。
后面将深入讲解IP协议、路由过程（包括策略路由）和邻居系统，整一个是同一有机体。这之前我们还会深入一些TC系统的研究，对TC的研究有助于巩固对数据包发送过程的理解；还有一个重要的是网桥的研究，网桥其实作为单独一章来讲解，并不会非常的深入，只是大体讲解网桥的过程，曾经参与过项目，将网桥和VLAN是合在一起的，具体可以参考LISA（http://lisa.mindbit.ro/）。