一、接收端
1、通过ehternetif_input
void ethernetif_input(struct netif *netif)
{ struct ethernetif *ethernetif; struct eth_hdr *ethhdr; struct pbuf *p; ethernetif = netif->state; /* move received packet into a new pbuf */ p = low_level_input(netif); //接收数据 /* no packet could be read, silently ignore this */ if (p == NULL) return; /* points to packet payload, which starts with an Ethernet header */ ethhdr = p->payload; switch (htons(ethhdr->type)) { /* IP or ARP packet? */ case ETHTYPE_IP: case ETHTYPE_ARP: #if PPPOE_SUPPORT /* PPPoE packet? */ case ETHTYPE_PPPOEDISC: case ETHTYPE_PPPOE: #endif /* PPPOE_SUPPORT */ /* full packet send to tcpip_thread to process */ if (netif->input(p, netif)!=ERR_OK) //调用etharp.c里的ethnet_input函数 { LWIP_DEBUGF(NETIF_DEBUG, ("ethernetif_input: IP input error\n")); pbuf_free(p); p = NULL; } break; default: pbuf_free(p); p = NULL; break; } }接下来看ethernet_input函数
err_t ethernet_input(struct pbuf *p, struct netif *netif) //注意这里传递进来的netif以后会根据这个判断是不是我这个网卡的数据 {
struct eth_hdr* ethhdr; /* points to packet payload, which starts with an Ethernet header */ ethhdr = p->payload; switch (htons(ethhdr->type)) { //不同协议调用不同函数 arp 0x0806 IP 0x0800 /* IP packet? */ case ETHTYPE_IP: #if ETHARP_TRUST_IP_MAC //如果使能了arp更新缓冲功能 /* update ARP table */ etharp_ip_input(netif, p); //更新arp列表 #endif /* ETHARP_TRUST_IP_MAC */ /* skip Ethernet header */ if(pbuf_header(p, -(s16_t)sizeof(struct eth_hdr))) { LWIP_ASSERT("Can't move over header in packet", 0); pbuf_free(p); p = NULL; } else { /* pass to IP layer */ ip_input(p, netif); //ip协议,调用IP处理函数 } break; case ETHTYPE_ARP: /* pass p to ARP module */ etharp_arp_input(netif, (struct eth_addr*)(netif->hwaddr), p); //arp协议,调用arp处理函数 break; #if PPPOE_SUPPORT case ETHTYPE_PPPOEDISC: /* PPP Over Ethernet Discovery Stage */ pppoe_disc_input(netif, p); break; case ETHTYPE_PPPOE: /* PPP Over Ethernet Session Stage */ pppoe_data_input(netif, p); break; #endif /* PPPOE_SUPPORT */ default: pbuf_free(p); p = NULL; break; } /* This means the pbuf is freed or consumed, so the caller doesn't have to free it again */ return ERR_OK; }接下来看 ip_input();
err_t
ip_input(struct pbuf *p, struct netif *inp) { struct ip_hdr *iphdr; struct netif *netif; u16_t iphdr_hlen; u16_t iphdr_len; #if LWIP_DHCP int check_ip_src=1; #endif /* LWIP_DHCP */ IP_STATS_INC(ip.recv); snmp_inc_ipinreceives(); /* identify the IP header */ iphdr = p->payload; //获取数据 if (IPH_V(iphdr) != 4) { LWIP_DEBUGF(IP_DEBUG | 1, ("IP packet dropped due to bad version number %"U16_F"\n", IPH_V(iphdr))); ip_debug_print(p); pbuf_free(p); IP_STATS_INC(ip.err); IP_STATS_INC(ip.drop); snmp_inc_ipinhdrerrors(); return ERR_OK; } /* 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 = ntohs(IPH_LEN(iphdr)); /* header length exceeds first pbuf length, or ip length exceeds total pbuf length? */ if ((iphdr_hlen > p->len) || (iphdr_len > p->tot_len)) { //判断获取的数据是否正确IP报头,数据大小 if (iphdr_hlen > p->len) LWIP_DEBUGF(IP_DEBUG | 2, ("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 | 2, ("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); snmp_inc_ipindiscards(); return ERR_OK; } /* verify checksum */#if CHECKSUM_CHECK_IP //如果使能了IP校验和 if (inet_chksum(iphdr, iphdr_hlen) != 0) { LWIP_DEBUGF(IP_DEBUG | 2, ("Checksum (0x%"X16_F") failed, IP packet dropped.\n", inet_chksum(iphdr, iphdr_hlen))); ip_debug_print(p); pbuf_free(p); IP_STATS_INC(ip.chkerr); IP_STATS_INC(ip.drop); snmp_inc_ipinhdrerrors(); return ERR_OK; } #endif /* Trim pbuf. This should have been done at the netif layer, * but we'll do it anyway just to be sure that its done. */ pbuf_realloc(p, iphdr_len); /* match packet against an interface, i.e. is this packet for us? */ #if LWIP_IGMP if (ip_addr_ismulticast(&(iphdr->dest))) { if ((inp->flags & NETIF_FLAG_IGMP) && (igmp_lookfor_group(inp, &(iphdr->dest)))) { netif = inp; } else { netif = NULL; } } else #endif /* LWIP_IGMP */ { /* 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 { //在netif链上寻找合适的网络接口 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", iphdr->dest.addr, netif->ip_addr.addr, iphdr->dest.addr & netif->netmask.addr, netif->ip_addr.addr & netif->netmask.addr, iphdr->dest.addr & ~(netif->netmask.addr))); /* interface is up and configured? */ if ((netif_is_up(netif)) && (!ip_addr_isany(&(netif->ip_addr)))) { //这里判断接口是否是up状态, /* unicast to this interface address? */ if (ip_addr_cmp(&(iphdr->dest), &(netif->ip_addr)) || /* or broadcast on this interface network address? */ ip_addr_isbroadcast(&(iphdr->dest), netif)) { //这里判断是否是目标地址,如果是,就跳出while LWIP_DEBUGF(IP_DEBUG, ("ip_input: packet accepted on interface %c%c\n", netif->name[0], netif->name[1])); /* break out of for loop */ break; } } if (first) { first = 0; netif = netif_list; } else { netif = netif->next; } if (netif == inp) { netif = netif->next; } } while(netif != NULL); } #if LWIP_DHCP /* 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 (netif == NULL) { /* remote port is DHCP server? */ if (IPH_PROTO(iphdr) == IP_PROTO_UDP) { LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE | 1, ("ip_input: UDP packet to DHCP client port %"U16_F"\n", ntohs(((struct udp_hdr *)((u8_t *)iphdr + iphdr_hlen))->dest))); if (ntohs(((struct udp_hdr *)((u8_t *)iphdr + iphdr_hlen))->dest) == DHCP_CLIENT_PORT) { LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE | 1, ("ip_input: DHCP packet accepted.\n")); netif = inp; check_ip_src = 0; } } } #endif /* LWIP_DHCP */ /* broadcast or multicast packet source address? Compliant with RFC 1122: 3.2.1.3 */ #if LWIP_DHCP if (check_ip_src) #endif /* LWIP_DHCP */ { if ((ip_addr_isbroadcast(&(iphdr->src), inp)) || (ip_addr_ismulticast(&(iphdr->src)))) { //判断是否是广播或多播,如果是,丢弃 /* packet source is not valid */ LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE | 1, ("ip_input: packet source is not valid.\n")); /* free (drop) packet pbufs */ pbuf_free(p); IP_STATS_INC(ip.drop); snmp_inc_ipinaddrerrors(); snmp_inc_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 | 1, ("ip_input: packet not for us.\n"));#if IP_FORWARD //如果只有一个网络接口卡,这里为0 /* non-broadcast packet? */ if (!ip_addr_isbroadcast(&(iphdr->dest), inp)) { /* try to forward IP packet on (other) interfaces */ ip_forward(p, iphdr, inp); } else #endif /* IP_FORWARD */ { snmp_inc_ipinaddrerrors(); snmp_inc_ipindiscards(); } pbuf_free(p); return ERR_OK; } /* packet consists of multiple fragments? */ if ((IPH_OFFSET(iphdr) & 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 ip_reass()\n", ntohs(IPH_ID(iphdr)), p->tot_len, ntohs(IPH_LEN(iphdr)), !!(IPH_OFFSET(iphdr) & htons(IP_MF)), (ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK)*8)); /* reassemble the packet*/ p = ip_reass(p); /* packet not fully reassembled yet? */ if (p == NULL) { return ERR_OK; } iphdr = p->payload; #else /* IP_REASSEMBLY == 0, no packet fragment reassembly code present */ pbuf_free(p); LWIP_DEBUGF(IP_DEBUG | 2, ("IP packet dropped since it was fragmented (0x%"X16_F") (while IP_REASSEMBLY == 0).\n", ntohs(IPH_OFFSET(iphdr)))); IP_STATS_INC(ip.opterr); IP_STATS_INC(ip.drop); /* unsupported protocol feature */ snmp_inc_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 | 2, ("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 */ snmp_inc_ipinunknownprotos(); return ERR_OK; } #endif /* IP_OPTIONS_ALLOWED == 0 */ /* send to upper layers */ LWIP_DEBUGF(IP_DEBUG, ("ip_input: \n")); ip_debug_print(p); LWIP_DEBUGF(IP_DEBUG, ("ip_input: p->len %"U16_F" p->tot_len %"U16_F"\n", p->len, p->tot_len)); #if LWIP_RAW /* raw input did not eat the packet? */ if (raw_input(p, inp) == 0) #endif /* LWIP_RAW */ { switch (IPH_PROTO(iphdr)) { //判断传输层用什么协议 #if LWIP_UDP case IP_PROTO_UDP: #if LWIP_UDPLITE case IP_PROTO_UDPLITE: #endif /* LWIP_UDPLITE */ snmp_inc_ipindelivers(); udp_input(p, inp); //UDP协议,调用UDP处理函数 break; #endif /* LWIP_UDP */ #if LWIP_TCP case IP_PROTO_TCP: snmp_inc_ipindelivers(); tcp_input(p, inp); //TCP协议,调用TCP处理函数 break; #endif /* LWIP_TCP */ #if LWIP_ICMP case IP_PROTO_ICMP: snmp_inc_ipindelivers(); icmp_input(p, inp); //ICMP协议,调用ICMP处理函数 break; #endif /* LWIP_ICMP */ #if LWIP_IGMP case IP_PROTO_IGMP: igmp_input(p,inp,&(iphdr->dest)); break; #endif /* LWIP_IGMP */ default: #if LWIP_ICMP /* send ICMP destination protocol unreachable unless is was a broadcast */ if (!ip_addr_isbroadcast(&(iphdr->dest), inp) && !ip_addr_ismulticast(&(iphdr->dest))) { p->payload = iphdr; icmp_dest_unreach(p, ICMP_DUR_PROTO); //发送ICMP报文,通知主机,有问题ICMP_DUR_NET = 0, /* net unreachable */ ICMP_DUR_HOST = 1, /* host unreachable */ ICMP_DUR_PROTO = 2, /* protocol unreachable */ ICMP_DUR_PORT = 3, /* port unreachable */ ICMP_DUR_FRAG = 4, /* fragmentation needed and DF set */ ICMP_DUR_SR = 5 /* source route failed */
} #endif /* LWIP_ICMP */ pbuf_free(p); LWIP_DEBUGF(IP_DEBUG | 2, ("Unsupported transport protocol %"U16_F"\n", IPH_PROTO(iphdr))); IP_STATS_INC(ip.proterr); IP_STATS_INC(ip.drop); snmp_inc_ipinunknownprotos(); } } return ERR_OK; }
接下来该分析一下udp_input了