/** * Processes ICMP input packets, called from ip_input(). * * Currently only processes icmp echo requests and sends * out the echo response. * * @param p the icmp echo request packet, p->payload pointing to the ip header * @param inp the netif on which this packet was received */ void icmp_input(struct pbuf *p, struct netif *inp) { u8_t type; #ifdef LWIP_DEBUG u8_t code; #endif /* LWIP_DEBUG */ struct icmp_echo_hdr *iecho; struct ip_hdr *iphdr; s16_t hlen; ICMP_STATS_INC(icmp.recv); snmp_inc_icmpinmsgs(); iphdr = (struct ip_hdr *)p->payload; hlen = IPH_HL(iphdr) * 4; if (pbuf_header(p, -hlen) || (p->tot_len < sizeof(u16_t)*2)) { LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%"U16_F" bytes) received\n", p->tot_len)); goto lenerr; } type = *((u8_t *)p->payload); #ifdef LWIP_DEBUG code = *(((u8_t *)p->payload)+1); #endif /* LWIP_DEBUG */ switch (type) { case ICMP_ER: /* This is OK, echo reply might have been parsed by a raw PCB (as obviously, an echo request has been sent, too). */ break; case ICMP_ECHO: #if !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING { int accepted = 1; #if !LWIP_MULTICAST_PING /* multicast destination address? */ if (ip_addr_ismulticast(¤t_iphdr_dest)) { accepted = 0; } #endif /* LWIP_MULTICAST_PING */ #if !LWIP_BROADCAST_PING /* broadcast destination address? */ if (ip_addr_isbroadcast(¤t_iphdr_dest, inp)) { accepted = 0; } #endif /* LWIP_BROADCAST_PING */ /* broadcast or multicast destination address not acceptd? */ if (!accepted) { LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast or broadcast pings\n")); ICMP_STATS_INC(icmp.err); pbuf_free(p); return; } } #endif /* !LWIP_MULTICAST_PING || !LWIP_BROADCAST_PING */ LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n")); if (p->tot_len < sizeof(struct icmp_echo_hdr)) { LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n")); goto lenerr; } if (inet_chksum_pbuf(p) != 0) { LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n")); pbuf_free(p); ICMP_STATS_INC(icmp.chkerr); snmp_inc_icmpinerrors(); return; } #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN if (pbuf_header(p, (PBUF_IP_HLEN + PBUF_LINK_HLEN))) { /* p is not big enough to contain link headers * allocate a new one and copy p into it */ struct pbuf *r; /* switch p->payload to ip header */ if (pbuf_header(p, hlen)) { LWIP_ASSERT("icmp_input: moving p->payload to ip header failed\n", 0); goto memerr; } /* allocate new packet buffer with space for link headers */ r = pbuf_alloc(PBUF_LINK, p->tot_len, PBUF_RAM); if (r == NULL) { LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: allocating new pbuf failed\n")); goto memerr; } LWIP_ASSERT("check that first pbuf can hold struct the ICMP header", (r->len >= hlen + sizeof(struct icmp_echo_hdr))); /* copy the whole packet including ip header */ if (pbuf_copy(r, p) != ERR_OK) { LWIP_ASSERT("icmp_input: copying to new pbuf failed\n", 0); goto memerr; } iphdr = (struct ip_hdr *)r->payload; /* switch r->payload back to icmp header */ if (pbuf_header(r, -hlen)) { LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0); goto memerr; } /* free the original p */ pbuf_free(p); /* we now have an identical copy of p that has room for link headers */ p = r; } else { /* restore p->payload to point to icmp header */ if (pbuf_header(p, -(s16_t)(PBUF_IP_HLEN + PBUF_LINK_HLEN))) { LWIP_ASSERT("icmp_input: restoring original p->payload failed\n", 0); goto memerr; } } #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */ /* At this point, all checks are OK. */ /* We generate an answer by switching the dest and src ip addresses, * setting the icmp type to ECHO_RESPONSE and updating the checksum. */ iecho = (struct icmp_echo_hdr *)p->payload; ip_addr_copy(iphdr->src, *ip_current_dest_addr()); ip_addr_copy(iphdr->dest, *ip_current_src_addr()); ICMPH_TYPE_SET(iecho, ICMP_ER); #if CHECKSUM_GEN_ICMP /* adjust the checksum */ if (iecho->chksum >= PP_HTONS(0xffffU - (ICMP_ECHO << 8))) { iecho->chksum += PP_HTONS(ICMP_ECHO << 8) + 1; } else { iecho->chksum += PP_HTONS(ICMP_ECHO << 8); } #else /* CHECKSUM_GEN_ICMP */ iecho->chksum = 0; #endif /* CHECKSUM_GEN_ICMP */ /* Set the correct TTL and recalculate the header checksum. */ IPH_TTL_SET(iphdr, ICMP_TTL); IPH_CHKSUM_SET(iphdr, 0); #if CHECKSUM_GEN_IP IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, IP_HLEN)); #endif /* CHECKSUM_GEN_IP */ ICMP_STATS_INC(icmp.xmit); /* increase number of messages attempted to send */ snmp_inc_icmpoutmsgs(); /* increase number of echo replies attempted to send */ snmp_inc_icmpoutechoreps(); if(pbuf_header(p, hlen)) { LWIP_ASSERT("Can't move over header in packet", 0); } else { err_t ret; /* send an ICMP packet, src addr is the dest addr of the curren packet */ ret = ip_output_if(p, ip_current_dest_addr(), IP_HDRINCL, ICMP_TTL, 0, IP_PROTO_ICMP, inp); if (ret != ERR_OK) { LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ip_output_if returned an error: %c.\n", ret)); } } break; default: LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %"S16_F" code %"S16_F" not supported.\n", (s16_t)type, (s16_t)code)); ICMP_STATS_INC(icmp.proterr); ICMP_STATS_INC(icmp.drop); } pbuf_free(p); return; lenerr: pbuf_free(p); ICMP_STATS_INC(icmp.lenerr); snmp_inc_icmpinerrors(); return; #if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN memerr: pbuf_free(p); ICMP_STATS_INC(icmp.err); snmp_inc_icmpinerrors(); return; #endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */ }
void icmp_input(struct pbuf *p, struct netif *inp) { unsigned char type; unsigned char code; struct icmp_echo_hdr *iecho; struct ip_hdr *iphdr; struct ip_addr tmpaddr; u16_t hlen; ICMP_STATS_INC(icmp.recv); snmp_inc_icmpinmsgs(); iphdr = p->payload; hlen = IPH_HL(iphdr) * 4; if (pbuf_header(p, -((s16_t)hlen)) || (p->tot_len < sizeof(u16_t)*2)) { LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: short ICMP (%u bytes) received\n", p->tot_len)); pbuf_free(p); ICMP_STATS_INC(icmp.lenerr); snmp_inc_icmpinerrors(); return; } type = *((u8_t *)p->payload); code = *(((u8_t *)p->payload)+1); switch (type) { case ICMP_ECHO: /* broadcast or multicast destination address? */ if (ip_addr_isbroadcast(&iphdr->dest, inp) || ip_addr_ismulticast(&iphdr->dest)) { LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: Not echoing to multicast or broadcast pings\n")); ICMP_STATS_INC(icmp.err); pbuf_free(p); return; } LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ping\n")); if (p->tot_len < sizeof(struct icmp_echo_hdr)) { LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: bad ICMP echo received\n")); pbuf_free(p); ICMP_STATS_INC(icmp.lenerr); snmp_inc_icmpinerrors(); return; } iecho = p->payload; if (inet_chksum_pbuf(p) != 0) { LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: checksum failed for received ICMP echo\n")); pbuf_free(p); ICMP_STATS_INC(icmp.chkerr); snmp_inc_icmpinerrors(); return; } tmpaddr.addr = iphdr->src.addr; iphdr->src.addr = iphdr->dest.addr; iphdr->dest.addr = tmpaddr.addr; ICMPH_TYPE_SET(iecho, ICMP_ER); /* adjust the checksum */ if (iecho->chksum >= htons(0xffff - (ICMP_ECHO << 8))) { iecho->chksum += htons(ICMP_ECHO << 8) + 1; } else { iecho->chksum += htons(ICMP_ECHO << 8); } ICMP_STATS_INC(icmp.xmit); /* increase number of messages attempted to send */ snmp_inc_icmpoutmsgs(); /* increase number of echo replies attempted to send */ snmp_inc_icmpoutechoreps(); pbuf_header(p, hlen); ip_output_if(p, &(iphdr->src), IP_HDRINCL, IPH_TTL(iphdr), 0, IP_PROTO_ICMP, inp); break; default: LWIP_DEBUGF(ICMP_DEBUG, ("icmp_input: ICMP type %d code %d not supported.\n", (int)type, (int)code)); ICMP_STATS_INC(icmp.proterr); ICMP_STATS_INC(icmp.drop); } pbuf_free(p); }