lwip分析-udp数据包接收过程详解
接收链路层数据
在以太网中断中接收到数据，最先调用
ethernetif_input(&g_stFslNetif0);
g_stFslNetif0是网卡接口结构体，数据处理过程为：
- 调用low_level_input，从网卡中获取数据
- 申请pbuf，将数据放进其中
- 将数据交给 netif->input，处理
（ netif->input在初始化的时候赋值为ethernet_input）
static struct pbuf * low_level_input(struct netif *netif)
{
struct pbuf *p = NULL;
ETH_BufferTypeDef RxBuff;
uint32_t framelength = 0;
struct pbuf_custom* custom_pbuf;
if (HAL_ETH_IsRxDataAvailable(&EthHandle))
{
HAL_ETH_GetRxDataBuffer(&EthHandle, &RxBuff);
HAL_ETH_GetRxDataLength(&EthHandle, &framelength);
/* Build Rx descriptor to be ready for next data reception */
HAL_ETH_BuildRxDescriptors(&EthHandle);
/* Invalidate data cache for ETH Rx Buffers */
SCB_InvalidateDCache_by_Addr((uint32_t *)RxBuff.buffer, framelength);
custom_pbuf = (struct pbuf_custom*)LWIP_MEMPOOL_ALLOC(RX_POOL);
custom_pbuf->custom_free_function = pbuf_free_custom;
p = pbuf_alloced_custom(PBUF_RAW, framelength, PBUF_REF, custom_pbuf, RxBuff.buffer, ETH_RX_BUFFER_SIZE);
return p;
}
else
{
return NULL;
}
}
void ethernetif_input(struct netif *netif)
{
err_t err;
struct pbuf *p;
/* move received packet into a new pbuf */
p = low_level_input(netif);
/* no packet could be read, silently ignore this */
if (p == NULL) return;
/* entry point to the LwIP stack */
err = netif->input(p, netif);
if (err != ERR_OK)
{
LWIP_DEBUGF(NETIF_DEBUG, ("ethernetif_input: IP input error\n"));
pbuf_free(p);
p = NULL;
}
}
这时候ethernet_input函数处理的是完整的以太网数据正，如下所示：
处理链路层数据
ethernet_input函数处理流程如下：
注意：上图中，只列举了，ip数据包，和arp数据包，实际上有很多种以太网数据报，lwip并没有全部实现。
其中描述以太网帧的结构式：
/** Ethernet header */
struct eth_hdr {
#if ETH_PAD_SIZE
PACK_STRUCT_FLD_8(u8_t padding[ETH_PAD_SIZE]);
#endif
PACK_STRUCT_FLD_S(struct eth_addr dest);
PACK_STRUCT_FLD_S(struct eth_addr src);
PACK_STRUCT_FIELD(u16_t type);
} PACK_STRUCT_STRUCT;
刚好是，目的地址，源地址，类型，共14个字节
需要注意的是通过pbuf_header， 改变p->payload指向的地址来改变去掉帧头
err_t
ethernet_input(struct pbuf *p, struct netif *netif)
{
struct eth_hdr* ethhdr;
u16_t type;
#if LWIP_ARP || ETHARP_SUPPORT_VLAN || LWIP_IPV6
s16_t ip_hdr_offset = SIZEOF_ETH_HDR;
#endif /* LWIP_ARP || ETHARP_SUPPORT_VLAN */
if (p->len <= SIZEOF_ETH_HDR) {
/* a packet with only an ethernet header (or less) is not valid for us */
ETHARP_STATS_INC(etharp.proterr);
ETHARP_STATS_INC(etharp.drop);
MIB2_STATS_NETIF_INC(netif, ifinerrors);
goto free_and_return;
}
/* points to packet payload, which starts with an Ethernet header */
ethhdr = (struct eth_hdr *)p->payload;
LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE,
("ethernet_input: dest:%"X8_F":%"X8_F":%"X8_F":%"X8_F":%"X8_F":%"X8_F", src:%"X8_F":%"X8_F":%"X8_F":%"X8_F":%"X8_F":%"X8_F", type:%"X16_F"\n",
(unsigned)ethhdr->dest.addr[0], (unsigned)ethhdr->dest.addr[1], (unsigned)ethhdr->dest.addr[2],
(unsigned)ethhdr->dest.addr[3], (unsigned)ethhdr->dest.addr[4], (unsigned)ethhdr->dest.addr[5],
(unsigned)ethhdr->src.addr[0], (unsigned)ethhdr->src.addr[1], (unsigned)ethhdr->src.addr[2],
(unsigned)ethhdr->src.addr[3], (unsigned)ethhdr->src.addr[4], (unsigned)ethhdr->src.addr[5],
lwip_htons(ethhdr->type)));
type = ethhdr->type;
#if ETHARP_SUPPORT_VLAN
if (type == PP_HTONS(ETHTYPE_VLAN)) {
struct eth_vlan_hdr *vlan = (struct eth_vlan_hdr*)(((char*)ethhdr) + SIZEOF_ETH_HDR);
if (p->len <= SIZEOF_ETH_HDR + SIZEOF_VLAN_HDR) {
/* a packet with only an ethernet/vlan header (or less) is not valid for us */
ETHARP_STATS_INC(etharp.proterr);
ETHARP_STATS_INC(etharp.drop);
MIB2_STATS_NETIF_INC(netif, ifinerrors);
goto free_and_return;
}
#if defined(LWIP_HOOK_VLAN_CHECK) || defined(ETHARP_VLAN_CHECK) || defined(ETHARP_VLAN_CHECK_FN) /* if not, allow all VLANs */
#ifdef LWIP_HOOK_VLAN_CHECK
if (!LWIP_HOOK_VLAN_CHECK(netif, ethhdr, vlan)) {
#elif defined(ETHARP_VLAN_CHECK_FN)
if (!ETHARP_VLAN_CHECK_FN(ethhdr, vlan)) {
#elif defined(ETHARP_VLAN_CHECK)
if (VLAN_ID(vlan) != ETHARP_VLAN_CHECK) {
#endif
/* silently ignore this packet: not for our VLAN */
pbuf_free(p);
return ERR_OK;
}
#endif /* defined(LWIP_HOOK_VLAN_CHECK) || defined(ETHARP_VLAN_CHECK) || defined(ETHARP_VLAN_CHECK_FN) */
type = vlan->tpid;
ip_hdr_offset = SIZEOF_ETH_HDR + SIZEOF_VLAN_HDR;
}
#endif /* ETHARP_SUPPORT_VLAN */
#if LWIP_ARP_FILTER_NETIF
netif = LWIP_ARP_FILTER_NETIF_FN(p, netif, lwip_htons(type));
#endif /* LWIP_ARP_FILTER_NETIF*/
if (ethhdr->dest.addr[0] & 1) {
/* this might be a multicast or broadcast packet */
if (ethhdr->dest.addr[0] == LL_IP4_MULTICAST_ADDR_0) {
#if LWIP_IPV4
if ((ethhdr->dest.addr[1] == LL_IP4_MULTICAST_ADDR_1) &&
(ethhdr->dest.addr[2] == LL_IP4_MULTICAST_ADDR_2)) {
/* mark the pbuf as link-layer multicast */
p->flags |= PBUF_FLAG_LLMCAST;
}
#endif /* LWIP_IPV4 */
}
#if LWIP_IPV6
else if ((ethhdr->dest.addr[0] == LL_IP6_MULTICAST_ADDR_0) &&
(ethhdr->dest.addr[1] == LL_IP6_MULTICAST_ADDR_1)) {
/* mark the pbuf as link-layer multicast */
p->flags |= PBUF_FLAG_LLMCAST;
}
#endif /* LWIP_IPV6 */
else if (eth_addr_cmp(ðhdr->dest, ðbroadcast)) {
/* mark the pbuf as link-layer broadcast */
p->flags |= PBUF_FLAG_LLBCAST;
}
}
switch (type) {
#if LWIP_IPV4 && LWIP_ARP
/* IP packet? */
case PP_HTONS(ETHTYPE_IP):
if (!(netif->flags & NETIF_FLAG_ETHARP)) {
goto free_and_return;
}
/* skip Ethernet header */
if ((p->len < ip_hdr_offset) || pbuf_header(p, (s16_t)-ip_hdr_offset)) {
LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING,
("ethernet_input: IPv4 packet dropped, too short (%"S16_F"/%"S16_F")\n",
p->tot_len, ip_hdr_offset));
LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("Can't move over header in packet"));
goto free_and_return;
} else {
/* pass to IP layer */
ip4_input(p, netif);
}
break;
case PP_HTONS(ETHTYPE_ARP):
if (!(netif->flags & NETIF_FLAG_ETHARP)) {
goto free_and_return;
}
/* skip Ethernet header */
if ((p->len < ip_hdr_offset) || pbuf_header(p, (s16_t)-ip_hdr_offset)) {
LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING,
("ethernet_input: ARP response packet dropped, too short (%"S16_F"/%"S16_F")\n",
p->tot_len, ip_hdr_offset));
LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE, ("Can't move over header in packet"));
ETHARP_STATS_INC(etharp.lenerr);
ETHARP_STATS_INC(etharp.drop);
goto free_and_return;
} else {
/* pass p to ARP module */
etharp_input(p, netif);
}
break;
#endif /* LWIP_IPV4 && LWIP_ARP */
#if PPPOE_SUPPORT
case PP_HTONS(ETHTYPE_PPPOEDISC): /* PPP Over Ethernet Discovery Stage */
pppoe_disc_input(netif, p);
break;
case PP_HTONS(ETHTYPE_PPPOE): /* PPP Over Ethernet Session Stage */
pppoe_data_input(netif, p);
break;
#endif /* PPPOE_SUPPORT */
#if LWIP_IPV6
case PP_HTONS(ETHTYPE_IPV6): /* IPv6 */
/* skip Ethernet header */
if ((p->len < ip_hdr_offset) || pbuf_header(p, (s16_t)-ip_hdr_offset)) {
LWIP_DEBUGF(ETHARP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING,
("ethernet_input: IPv6 packet dropped, too short (%"S16_F"/%"S16_F")\n",
p->tot_len, ip_hdr_offset));
goto free_and_return;
} else {
/* pass to IPv6 layer */
ip6_input(p, netif);
}
break;
#endif /* LWIP_IPV6 */
case PP_HTONS(ETHERTYPE_SADP):
/* pass p to SDAP module */
etharp_sadp_input(netif, (struct ether_hdaddr*)(netif->hwaddr), p); //hd
break;
default:
#ifdef LWIP_HOOK_UNKNOWN_ETH_PROTOCOL
if(LWIP_HOOK_UNKNOWN_ETH_PROTOCOL(p, netif) == ERR_OK) {
break;
}
#endif
ETHARP_STATS_INC(etharp.proterr);
ETHARP_STATS_INC(etharp.drop);
MIB2_STATS_NETIF_INC(netif, ifinunknownprotos);
goto free_and_return;
}
/* This means the pbuf is freed or consumed,
so the caller doesn't have to free it again */
return ERR_OK;
free_and_return:
pbuf_free(p);
return ERR_OK;
}
处理ip数据报
因为udp并不是点对点的，所以，udp存在，多播和组播
解析组播的数据条件是,目的地址是组播地址
网卡开启了组播，并且组播地址，加入了网卡的组播链表
inp->flags & NETIF_FLAG_IGMP) && (igmp_lookfor_group(inp, ip4_current_dest_addr()
（有的硬件会自动过滤组播，这种情况下，是无法收到组播的）
err_t
ip4_input(struct pbuf *p, struct netif *inp)
{
struct ip_hdr *iphdr;
struct netif *netif;
u16_t iphdr_hlen;
u16_t iphdr_len;
#if IP_ACCEPT_LINK_LAYER_ADDRESSING || LWIP_IGMP
int check_ip_src = 1;
#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING || LWIP_IGMP */
IP_STATS_INC(ip.recv);
MIB2_STATS_INC(mib2.ipinreceives);
/* identify the IP header */
iphdr = (struct ip_hdr *)p->payload;
if (IPH_V(iphdr) != 4) {
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_WARNING, ("IP packet dropped due to bad version number %"U16_F"\n", (u16_t)IPH_V(iphdr)));
ip4_debug_print(p);
pbuf_free(p);
IP_STATS_INC(ip.err);
IP_STATS_INC(ip.drop);
MIB2_STATS_INC(mib2.ipinhdrerrors);
return ERR_OK;
}
#ifdef LWIP_HOOK_IP4_INPUT
if (LWIP_HOOK_IP4_INPUT(p, inp)) {
/* the packet has been eaten */
return ERR_OK;
}
#endif
/* obtain IP header length in number of 32-bit words */
iphdr_hlen = IPH_HL(iphdr);
/* calculate IP header length in bytes */
iphdr_hlen *= 4;
/* obtain ip length in bytes */
iphdr_len = lwip_ntohs(IPH_LEN(iphdr));
/* Trim pbuf. This is especially required for packets < 60 bytes. */
if (iphdr_len < p->tot_len) {
pbuf_realloc(p, iphdr_len);
}
/* header length exceeds first pbuf length, or ip length exceeds total pbuf length? */
if ((iphdr_hlen > p->len) || (iphdr_len > p->tot_len) || (iphdr_hlen < IP_HLEN)) {
if (iphdr_hlen < IP_HLEN) {
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
("ip4_input: short IP header (%"U16_F" bytes) received, IP packet dropped\n", iphdr_hlen));
}
if (iphdr_hlen > p->len) {
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
("IP header (len %"U16_F") does not fit in first pbuf (len %"U16_F"), IP packet dropped.\n",
iphdr_hlen, p->len));
}
if (iphdr_len > p->tot_len) {
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
("IP (len %"U16_F") is longer than pbuf (len %"U16_F"), IP packet dropped.\n",
iphdr_len, p->tot_len));
}
/* free (drop) packet pbufs */
pbuf_free(p);
IP_STATS_INC(ip.lenerr);
IP_STATS_INC(ip.drop);
MIB2_STATS_INC(mib2.ipindiscards);
return ERR_OK;
}
/* verify checksum */
#if CHECKSUM_CHECK_IP
IF__NETIF_CHECKSUM_ENABLED(inp, NETIF_CHECKSUM_CHECK_IP) {
if (inet_chksum(iphdr, iphdr_hlen) != 0) {
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
("Checksum (0x%"X16_F") failed, IP packet dropped.\n", inet_chksum(iphdr, iphdr_hlen)));
ip4_debug_print(p);
pbuf_free(p);
IP_STATS_INC(ip.chkerr);
IP_STATS_INC(ip.drop);
MIB2_STATS_INC(mib2.ipinhdrerrors);
return ERR_OK;
}
}
#endif
/* copy IP addresses to aligned ip_addr_t */
ip_addr_copy_from_ip4(ip_data.current_iphdr_dest, iphdr->dest);
ip_addr_copy_from_ip4(ip_data.current_iphdr_src, iphdr->src);
/* match packet against an interface, i.e. is this packet for us? */
if (ip4_addr_ismulticast(ip4_current_dest_addr())) {
#if LWIP_IGMP
if ((inp->flags & NETIF_FLAG_IGMP) && (igmp_lookfor_group(inp, ip4_current_dest_addr()))) {
/* IGMP snooping switches need 0.0.0.0 to be allowed as source address (RFC 4541) */
ip4_addr_t allsystems;
IP4_ADDR(&allsystems, 224, 0, 0, 1);
if (ip4_addr_cmp(ip4_current_dest_addr(), &allsystems) &&
ip4_addr_isany(ip4_current_src_addr())) {
check_ip_src = 0;
}
netif = inp;
} else {
netif = NULL;
}
#else /* LWIP_IGMP */
if ((netif_is_up(inp)) && (!ip4_addr_isany_val(*netif_ip4_addr(inp)))) {
netif = inp;
} else {
netif = NULL;
}
#endif /* LWIP_IGMP */
} else {
/* start trying with inp. if that's not acceptable, start walking the
list of configured netifs.
'first' is used as a boolean to mark whether we started walking the list */
int first = 1;
netif = inp;
do {
LWIP_DEBUGF(IP_DEBUG, ("ip_input: iphdr->dest 0x%"X32_F" netif->ip_addr 0x%"X32_F" (0x%"X32_F", 0x%"X32_F", 0x%"X32_F")\n",
ip4_addr_get_u32(&iphdr->dest), ip4_addr_get_u32(netif_ip4_addr(netif)),
ip4_addr_get_u32(&iphdr->dest) & ip4_addr_get_u32(netif_ip4_netmask(netif)),
ip4_addr_get_u32(netif_ip4_addr(netif)) & ip4_addr_get_u32(netif_ip4_netmask(netif)),
ip4_addr_get_u32(&iphdr->dest) & ~ip4_addr_get_u32(netif_ip4_netmask(netif))));
/* interface is up and configured? */
if ((netif_is_up(netif)) && (!ip4_addr_isany_val(*netif_ip4_addr(netif)))) {
/* unicast to this interface address? */
if (ip4_addr_cmp(ip4_current_dest_addr(), netif_ip4_addr(netif)) ||
/* or broadcast on this interface network address? */
ip4_addr_isbroadcast(ip4_current_dest_addr(), netif)
#if LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF
|| (ip4_addr_get_u32(ip4_current_dest_addr()) == PP_HTONL(IPADDR_LOOPBACK))
#endif /* LWIP_NETIF_LOOPBACK && !LWIP_HAVE_LOOPIF */
) {
LWIP_DEBUGF(IP_DEBUG, ("ip4_input: packet accepted on interface %c%c\n",
netif->name[0], netif->name[1]));
/* break out of for loop */
break;
}
#if LWIP_AUTOIP
/* connections to link-local addresses must persist after changing
the netif's address (RFC3927 ch. 1.9) */
if (autoip_accept_packet(netif, ip4_current_dest_addr())) {
LWIP_DEBUGF(IP_DEBUG, ("ip4_input: LLA packet accepted on interface %c%c\n",
netif->name[0], netif->name[1]));
/* break out of for loop */
break;
}
#endif /* LWIP_AUTOIP */
}
if (first) {
#if !LWIP_NETIF_LOOPBACK || LWIP_HAVE_LOOPIF
/* Packets sent to the loopback address must not be accepted on an
* interface that does not have the loopback address assigned to it,
* unless a non-loopback interface is used for loopback traffic. */
if (ip4_addr_isloopback(ip4_current_dest_addr())) {
netif = NULL;
break;
}
#endif /* !LWIP_NETIF_LOOPBACK || LWIP_HAVE_LOOPIF */
first = 0;
netif = netif_list;
} else {
netif = netif->next;
}
if (netif == inp) {
netif = netif->next;
}
} while (netif != NULL);
}
#if IP_ACCEPT_LINK_LAYER_ADDRESSING
/* Pass DHCP messages regardless of destination address. DHCP traffic is addressed
* using link layer addressing (such as Ethernet MAC) so we must not filter on IP.
* According to RFC 1542 section 3.1.1, referred by RFC 2131).
*
* If you want to accept private broadcast communication while a netif is down,
* define LWIP_IP_ACCEPT_UDP_PORT(dst_port), e.g.:
*
* #define LWIP_IP_ACCEPT_UDP_PORT(dst_port) ((dst_port) == PP_NTOHS(12345))
*/
if (netif == NULL) {
/* remote port is DHCP server? */
if (IPH_PROTO(iphdr) == IP_PROTO_UDP) {
struct udp_hdr *udphdr = (struct udp_hdr *)((u8_t *)iphdr + iphdr_hlen);
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip4_input: UDP packet to DHCP client port %"U16_F"\n",
lwip_ntohs(udphdr->dest)));
if (IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(udphdr->dest)) {
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip4_input: DHCP packet accepted.\n"));
netif = inp;
check_ip_src = 0;
}
}
}
#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
/* broadcast or multicast packet source address? Compliant with RFC 1122: 3.2.1.3 */
#if LWIP_IGMP || IP_ACCEPT_LINK_LAYER_ADDRESSING
if (check_ip_src
#if IP_ACCEPT_LINK_LAYER_ADDRESSING
/* DHCP servers need 0.0.0.0 to be allowed as source address (RFC 1.1.2.2: 3.2.1.3/a) */
&& !ip4_addr_isany_val(*ip4_current_src_addr())
#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
)
#endif /* LWIP_IGMP || IP_ACCEPT_LINK_LAYER_ADDRESSING */
{
if ((ip4_addr_isbroadcast(ip4_current_src_addr(), inp)) ||
(ip4_addr_ismulticast(ip4_current_src_addr()))) {
/* packet source is not valid */
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING, ("ip4_input: packet source is not valid.\n"));
/* free (drop) packet pbufs */
pbuf_free(p);
IP_STATS_INC(ip.drop);
MIB2_STATS_INC(mib2.ipinaddrerrors);
MIB2_STATS_INC(mib2.ipindiscards);
return ERR_OK;
}
}
/* packet not for us? */
if (netif == NULL) {
/* packet not for us, route or discard */
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip4_input: packet not for us.\n"));
#if IP_FORWARD
/* non-broadcast packet? */
if (!ip4_addr_isbroadcast(ip4_current_dest_addr(), inp)) {
/* try to forward IP packet on (other) interfaces */
ip4_forward(p, iphdr, inp);
} else
#endif /* IP_FORWARD */
{
IP_STATS_INC(ip.drop);
MIB2_STATS_INC(mib2.ipinaddrerrors);
MIB2_STATS_INC(mib2.ipindiscards);
}
pbuf_free(p);
return ERR_OK;
}
/* packet consists of multiple fragments? */
if ((IPH_OFFSET(iphdr) & PP_HTONS(IP_OFFMASK | IP_MF)) != 0) {
#if IP_REASSEMBLY /* packet fragment reassembly code present? */
LWIP_DEBUGF(IP_DEBUG, ("IP packet is a fragment (id=0x%04"X16_F" tot_len=%"U16_F" len=%"U16_F" MF=%"U16_F" offset=%"U16_F"), calling ip4_reass()\n",
lwip_ntohs(IPH_ID(iphdr)), p->tot_len, lwip_ntohs(IPH_LEN(iphdr)), (u16_t)!!(IPH_OFFSET(iphdr) & PP_HTONS(IP_MF)), (u16_t)((lwip_ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK)*8)));
/* reassemble the packet*/
p = ip4_reass(p);
/* packet not fully reassembled yet? */
if (p == NULL) {
return ERR_OK;
}
iphdr = (struct ip_hdr *)p->payload;
#else /* IP_REASSEMBLY == 0, no packet fragment reassembly code present */
pbuf_free(p);
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since it was fragmented (0x%"X16_F") (while IP_REASSEMBLY == 0).\n",
lwip_ntohs(IPH_OFFSET(iphdr))));
IP_STATS_INC(ip.opterr);
IP_STATS_INC(ip.drop);
/* unsupported protocol feature */
MIB2_STATS_INC(mib2.ipinunknownprotos);
return ERR_OK;
#endif /* IP_REASSEMBLY */
}
#if IP_OPTIONS_ALLOWED == 0 /* no support for IP options in the IP header? */
#if LWIP_IGMP
/* there is an extra "router alert" option in IGMP messages which we allow for but do not police */
if ((iphdr_hlen > IP_HLEN) && (IPH_PROTO(iphdr) != IP_PROTO_IGMP)) {
#else
if (iphdr_hlen > IP_HLEN) {
#endif /* LWIP_IGMP */
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since there were IP options (while IP_OPTIONS_ALLOWED == 0).\n"));
pbuf_free(p);
IP_STATS_INC(ip.opterr);
IP_STATS_INC(ip.drop);
/* unsupported protocol feature */
MIB2_STATS_INC(mib2.ipinunknownprotos);
return ERR_OK;
}
#endif /* IP_OPTIONS_ALLOWED == 0 */
/* send to upper layers */
LWIP_DEBUGF(IP_DEBUG, ("ip4_input: \n"));
ip4_debug_print(p);
LWIP_DEBUGF(IP_DEBUG, ("ip4_input: p->len %"U16_F" p->tot_len %"U16_F"\n", p->len, p->tot_len));
ip_data.current_netif = netif;
ip_data.current_input_netif = inp;
ip_data.current_ip4_header = iphdr;
ip_data.current_ip_header_tot_len = IPH_HL(iphdr) * 4;
#if LWIP_RAW
/* raw input did not eat the packet? */
if (raw_input(p, inp) == 0)
#endif /* LWIP_RAW */
{
pbuf_header(p, -(s16_t)iphdr_hlen); /* Move to payload, no check necessary. */
switch (IPH_PROTO(iphdr)) {
#if LWIP_UDP
case IP_PROTO_UDP:
#if LWIP_UDPLITE
case IP_PROTO_UDPLITE:
#endif /* LWIP_UDPLITE */
MIB2_STATS_INC(mib2.ipindelivers);
udp_input(p, inp);
break;
#endif /* LWIP_UDP */
#if LWIP_TCP
case IP_PROTO_TCP:
MIB2_STATS_INC(mib2.ipindelivers);
tcp_input(p, inp);
break;
#endif /* LWIP_TCP */
#if LWIP_ICMP
case IP_PROTO_ICMP:
MIB2_STATS_INC(mib2.ipindelivers);
icmp_input(p, inp);
break;
#endif /* LWIP_ICMP */
#if LWIP_IGMP
case IP_PROTO_IGMP:
igmp_input(p, inp, ip4_current_dest_addr());
break;
#endif /* LWIP_IGMP */
default:
#if LWIP_ICMP
/* send ICMP destination protocol unreachable unless is was a broadcast */
if (!ip4_addr_isbroadcast(ip4_current_dest_addr(), netif) &&
!ip4_addr_ismulticast(ip4_current_dest_addr())) {
pbuf_header_force(p, iphdr_hlen); /* Move to ip header, no check necessary. */
p->payload = iphdr;
icmp_dest_unreach(p, ICMP_DUR_PROTO);
}
#endif /* LWIP_ICMP */
pbuf_free(p);
LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("Unsupported transport protocol %"U16_F"\n", (u16_t)IPH_PROTO(iphdr)));
IP_STATS_INC(ip.proterr);
IP_STATS_INC(ip.drop);
MIB2_STATS_INC(mib2.ipinunknownprotos);
}
}
/* @todo: this is not really necessary... */
ip_data.current_netif = NULL;
ip_data.current_input_netif = NULL;
ip_data.current_ip4_header = NULL;
ip_data.current_ip_header_tot_len = 0;
ip4_addr_set_any(ip4_current_src_addr());
ip4_addr_set_any(ip4_current_dest_addr());
return ERR_OK;
}
处理udp数据报
void
udp_input(struct pbuf *p, struct netif *inp)
{
struct udp_hdr *udphdr;
struct udp_pcb *pcb, *prev;
struct udp_pcb *uncon_pcb;
u16_t src, dest;
u8_t broadcast;
u8_t for_us = 0;
LWIP_UNUSED_ARG(inp);
PERF_START;
UDP_STATS_INC(udp.recv);
/* Check minimum length (UDP header) */
if (p->len < UDP_HLEN) {
/* drop short packets */
LWIP_DEBUGF(UDP_DEBUG,
("udp_input: short UDP datagram (%"U16_F" bytes) discarded\n", p->tot_len));
UDP_STATS_INC(udp.lenerr);
UDP_STATS_INC(udp.drop);
MIB2_STATS_INC(mib2.udpinerrors);
pbuf_free(p);
goto end;
}
udphdr = (struct udp_hdr *)p->payload;
/* is broadcast packet ? */
broadcast = ip_addr_isbroadcast(ip_current_dest_addr(), ip_current_netif());
LWIP_DEBUGF(UDP_DEBUG, ("udp_input: received datagram of length %"U16_F"\n", p->tot_len));
/* convert src and dest ports to host byte order */
src = lwip_ntohs(udphdr->src);
dest = lwip_ntohs(udphdr->dest);
udp_debug_print(udphdr);
/* print the UDP source and destination */
LWIP_DEBUGF(UDP_DEBUG, ("udp ("));
ip_addr_debug_print(UDP_DEBUG, ip_current_dest_addr());
LWIP_DEBUGF(UDP_DEBUG, (", %"U16_F") <-- (", lwip_ntohs(udphdr->dest)));
ip_addr_debug_print(UDP_DEBUG, ip_current_src_addr());
LWIP_DEBUGF(UDP_DEBUG, (", %"U16_F")\n", lwip_ntohs(udphdr->src)));
pcb = NULL;
prev = NULL;
uncon_pcb = NULL;
/* Iterate through the UDP pcb list for a matching pcb.
* 'Perfect match' pcbs (connected to the remote port & ip address) are
* preferred. If no perfect match is found, the first unconnected pcb that
* matches the local port and ip address gets the datagram. */
for (pcb = udp_pcbs; pcb != NULL; pcb = pcb->next) {
/* print the PCB local and remote address */
LWIP_DEBUGF(UDP_DEBUG, ("pcb ("));
ip_addr_debug_print(UDP_DEBUG, &pcb->local_ip);
LWIP_DEBUGF(UDP_DEBUG, (", %"U16_F") <-- (", pcb->local_port));
ip_addr_debug_print(UDP_DEBUG, &pcb->remote_ip);
LWIP_DEBUGF(UDP_DEBUG, (", %"U16_F")\n", pcb->remote_port));
/* compare PCB local addr+port to UDP destination addr+port */
if ((pcb->local_port == dest) &&
(udp_input_local_match(pcb, inp, broadcast) != 0)) {
if (((pcb->flags & UDP_FLAGS_CONNECTED) == 0) &&
((uncon_pcb == NULL)
#if SO_REUSE
/* prefer specific IPs over cath-all */
|| !ip_addr_isany(&pcb->local_ip)
#endif /* SO_REUSE */
)) {
/* the first unconnected matching PCB */
uncon_pcb = pcb;
}
/* compare PCB remote addr+port to UDP source addr+port */
if ((pcb->remote_port == src) &&
(ip_addr_isany_val(pcb->remote_ip) ||
ip_addr_cmp(&pcb->remote_ip, ip_current_src_addr()))) {
/* the first fully matching PCB */
if (prev != NULL) {
/* move the pcb to the front of udp_pcbs so that is
found faster next time */
prev->next = pcb->next;
pcb->next = udp_pcbs;
udp_pcbs = pcb;
} else {
UDP_STATS_INC(udp.cachehit);
}
break;
}
}
prev = pcb;
}
/* no fully matching pcb found? then look for an unconnected pcb */
if (pcb == NULL) {
pcb = uncon_pcb;
}
/* Check checksum if this is a match or if it was directed at us. */
if (pcb != NULL) {
for_us = 1;
} else {
#if LWIP_IPV6
if (ip_current_is_v6()) {
for_us = netif_get_ip6_addr_match(inp, ip6_current_dest_addr()) >= 0;
}
#endif /* LWIP_IPV6 */
#if LWIP_IPV4
if (!ip_current_is_v6()) {
for_us = ip4_addr_cmp(netif_ip4_addr(inp), ip4_current_dest_addr());
}
#endif /* LWIP_IPV4 */
}
if (for_us) {
LWIP_DEBUGF(UDP_DEBUG | LWIP_DBG_TRACE, ("udp_input: calculating checksum\n"));
#if CHECKSUM_CHECK_UDP
IF__NETIF_CHECKSUM_ENABLED(inp, CHECKSUM_CHECK_UDP) {
#if LWIP_UDPLITE
if (ip_current_header_proto() == IP_PROTO_UDPLITE) {
/* Do the UDP Lite checksum */
u16_t chklen = lwip_ntohs(udphdr->len);
if (chklen < sizeof(struct udp_hdr)) {
if (chklen == 0) {
/* For UDP-Lite, checksum length of 0 means checksum
over the complete packet (See RFC 3828 chap. 3.1) */
chklen = p->tot_len;
} else {
/* At least the UDP-Lite header must be covered by the
checksum! (Again, see RFC 3828 chap. 3.1) */
goto chkerr;
}
}
if (ip_chksum_pseudo_partial(p, IP_PROTO_UDPLITE,
p->tot_len, chklen,
ip_current_src_addr(), ip_current_dest_addr()) != 0) {
goto chkerr;
}
} else
#endif /* LWIP_UDPLITE */
{
if (udphdr->chksum != 0) {
if (ip_chksum_pseudo(p, IP_PROTO_UDP, p->tot_len,
ip_current_src_addr(),
ip_current_dest_addr()) != 0) {
goto chkerr;
}
}
}
}
#endif /* CHECKSUM_CHECK_UDP */
if (pbuf_header(p, -UDP_HLEN)) {
/* Can we cope with this failing? Just assert for now */
LWIP_ASSERT("pbuf_header failed\n", 0);
UDP_STATS_INC(udp.drop);
MIB2_STATS_INC(mib2.udpinerrors);
pbuf_free(p);
goto end;
}
if (pcb != NULL) {
MIB2_STATS_INC(mib2.udpindatagrams);
#if SO_REUSE && SO_REUSE_RXTOALL
if (ip_get_option(pcb, SOF_REUSEADDR) &&
(broadcast || ip_addr_ismulticast(ip_current_dest_addr()))) {
/* pass broadcast- or multicast packets to all multicast pcbs
if SOF_REUSEADDR is set on the first match */
struct udp_pcb *mpcb;
u8_t p_header_changed = 0;
s16_t hdrs_len = (s16_t)(ip_current_header_tot_len() + UDP_HLEN);
for (mpcb = udp_pcbs; mpcb != NULL; mpcb = mpcb->next) {
if (mpcb != pcb) {
/* compare PCB local addr+port to UDP destination addr+port */
if ((mpcb->local_port == dest) &&
(udp_input_local_match(mpcb, inp, broadcast) != 0)) {
/* pass a copy of the packet to all local matches */
if (mpcb->recv != NULL) {
struct pbuf *q;
/* for that, move payload to IP header again */
if (p_header_changed == 0) {
pbuf_header_force(p, hdrs_len);
p_header_changed = 1;
}
q = pbuf_alloc(PBUF_RAW, p->tot_len, PBUF_RAM);
if (q != NULL) {
err_t err = pbuf_copy(q, p);
if (err == ERR_OK) {
/* move payload to UDP data */
pbuf_header(q, -hdrs_len);
mpcb->recv(mpcb->recv_arg, mpcb, q, ip_current_src_addr(), src);
}
}
}
}
}
}
if (p_header_changed) {
/* and move payload to UDP data again */
pbuf_header(p, -hdrs_len);
}
}
#endif /* SO_REUSE && SO_REUSE_RXTOALL */
/* callback */
if (pcb->recv != NULL) {
/* now the recv function is responsible for freeing p */
pcb->recv(pcb->recv_arg, pcb, p, ip_current_src_addr(), src);
} else {
/* no recv function registered? then we have to free the pbuf! */
pbuf_free(p);
goto end;
}
} else {
LWIP_DEBUGF(UDP_DEBUG | LWIP_DBG_TRACE, ("udp_input: not for us.\n"));
#if LWIP_ICMP || LWIP_ICMP6
/* No match was found, send ICMP destination port unreachable unless
destination address was broadcast/multicast. */
if (!broadcast && !ip_addr_ismulticast(ip_current_dest_addr())) {
/* move payload pointer back to ip header */
pbuf_header_force(p, (s16_t)(ip_current_header_tot_len() + UDP_HLEN));
icmp_port_unreach(ip_current_is_v6(), p);
}
#endif /* LWIP_ICMP || LWIP_ICMP6 */
UDP_STATS_INC(udp.proterr);
UDP_STATS_INC(udp.drop);
MIB2_STATS_INC(mib2.udpnoports);
pbuf_free(p);
}
} else {
pbuf_free(p);
}
end:
PERF_STOP("udp_input");
return;
#if CHECKSUM_CHECK_UDP
chkerr:
LWIP_DEBUGF(UDP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
("udp_input: UDP (or UDP Lite) datagram discarded due to failing checksum\n"));
UDP_STATS_INC(udp.chkerr);
UDP_STATS_INC(udp.drop);
MIB2_STATS_INC(mib2.udpinerrors);
pbuf_free(p);
PERF_STOP("udp_input");
#endif /* CHECKSUM_CHECK_UDP */
}
总结来看，就是，ip层是使用源和目的ip地址，来区分数据是不是发给自己的（判断发给自身网卡的）
udp层使用源和目的端口号，来判断，数据是发给udp那个进程的
用户数据处理
- 从pbuf拷贝出数据，并处理数据
memcpy((char *)&user_buff,(pkt_buf->payload),pkt_buf->len); - 释放pbuf