/* ether.c - Raw Ethernet stuff * Author: Kees J. Bot * 16 Dec 2000 */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "arp.h" #include "dhcpd.h" static ether_addr_t BCAST_ETH = {{ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }}; #define BCAST_IP htonl(0xFFFFFFFFUL) #define LOCALHOST htonl(0x7F000001UL) static u16_t udp_cksum(ipaddr_t src, ipaddr_t dst, udp_hdr_t *udp) { /* Compute the checksum of an UDP packet plus data. */ struct udp_pseudo { ipaddr_t src, dst; u8_t zero, proto; u16_t length; } pseudo; size_t len; /* Fill in the UDP pseudo header that must be prefixed to the UDP * packet to compute the checksum of the whole thing. */ pseudo.src= src; pseudo.dst= dst; pseudo.zero= 0; pseudo.proto= IPPROTO_UDP; pseudo.length= udp->uh_length; len= ntohs(udp->uh_length); if (len & 1) { /* Length is odd? Pad with a zero. */ B(udp)[len++]= 0; } return oneC_sum(oneC_sum(0, &pseudo, sizeof(pseudo)), udp, len); } void udp2ether(buf_t *bp, network_t *np) { /* Transform a packet in UDP format to raw Ethernet. Ignore the UDP * addresses, always broadcast from 0.0.0.0. */ udp_io_hdr_t udpio; /* Save the UDP I/O header. */ udpio= *bp->udpio; /* Fill in the Ethernet, IP and UDP headers. */ bp->eth->eh_dst= BCAST_ETH; bp->eth->eh_src= np->eth; bp->eth->eh_proto= htons(ETH_IP_PROTO); bp->ip->ih_vers_ihl= 0x45; bp->ip->ih_tos= 0; bp->ip->ih_length= htons(sizeof(ip_hdr_t) + sizeof(udp_hdr_t) + udpio.uih_data_len); bp->ip->ih_id= 0; bp->ip->ih_flags_fragoff= ntohs(0x4000); bp->ip->ih_ttl= IP_MAX_TTL; bp->ip->ih_proto= IPPROTO_UDP; bp->ip->ih_hdr_chk= 0; bp->ip->ih_src= 0; bp->ip->ih_dst= BCAST_IP; bp->ip->ih_hdr_chk= ~oneC_sum(0, bp->ip, sizeof(*bp->ip)); bp->udp->uh_src_port= udpio.uih_src_port; bp->udp->uh_dst_port= udpio.uih_dst_port; bp->udp->uh_length= htons(sizeof(udp_hdr_t) + udpio.uih_data_len); bp->udp->uh_chksum= 0; bp->udp->uh_chksum= ~udp_cksum(bp->ip->ih_src, bp->ip->ih_dst, bp->udp); } int ether2udp(buf_t *bp) { /* Transform an UDP packet read from raw Ethernet to normal UDP. * Return true iff the packet is indeed UDP and has no errors. */ udp_io_hdr_t udpio; if (bp->eth->eh_proto != htons(ETH_IP_PROTO) || bp->ip->ih_vers_ihl != 0x45 || bp->ip->ih_proto != IPPROTO_UDP || oneC_sum(0, bp->ip, 20) != (u16_t) ~0 || udp_cksum(bp->ip->ih_src, bp->ip->ih_dst, bp->udp) != (u16_t) ~0 ) { /* Not UDP/IP or checksums bad. */ return 0; } udpio.uih_src_addr= bp->ip->ih_src; udpio.uih_dst_addr= bp->ip->ih_dst; udpio.uih_src_port= bp->udp->uh_src_port; udpio.uih_dst_port= bp->udp->uh_dst_port; udpio.uih_ip_opt_len= 0; udpio.uih_data_len= ntohs(bp->udp->uh_length) - sizeof(udp_hdr_t); *bp->udpio= udpio; return 1; } void make_arp(buf_t *bp, network_t *np) { /* Create an ARP packet to query for my IP address. */ arp46_t *arp= (arp46_t *) bp->eth; memset(arp, 0, sizeof(*arp)); arp->dstaddr= BCAST_ETH; arp->srcaddr= np->eth; arp->ethtype= htons(ETH_ARP_PROTO); arp->hdr= htons(ARP_ETHERNET); arp->pro= htons(ETH_IP_PROTO); arp->op= htons(ARP_REQUEST); arp->hln= 6; arp->pln= 4; arp->sha= np->eth; memcpy(arp->spa, &np->ip, sizeof(np->ip)); memcpy(arp->tpa, &np->ip, sizeof(np->ip)); } int is_arp_me(buf_t *bp, network_t *np) { /* True iff an ARP packet is a reply from someone else with an address I * thought was mine. (That's like, bad.) */ arp46_t *arp= (arp46_t *) bp->eth; if (arp->ethtype == htons(ETH_ARP_PROTO) && arp->hdr == htons(ARP_ETHERNET) && arp->pro == htons(ETH_IP_PROTO) && arp->op == htons(ARP_REPLY) && memcmp(&arp->spa, &np->ip, sizeof(np->ip)) == 0 && memcmp(&arp->sha, &np->eth, sizeof(np->eth)) != 0 ) { np->conflict= arp->sha; return 1; } return 0; } void icmp_solicit(buf_t *bp) { /* Fill in a router solicitation ICMP packet. */ icmp_hdr_t *icmp= (icmp_hdr_t *) (bp->ip + 1); bp->ip->ih_vers_ihl= 0x45; bp->ip->ih_dst= BCAST_IP; icmp->ih_type= ICMP_TYPE_ROUTE_SOL; icmp->ih_code= 0; icmp->ih_hun.ihh_unused= 0; icmp->ih_chksum= 0; icmp->ih_chksum= ~oneC_sum(0, icmp, 8); } void icmp_advert(buf_t *bp, network_t *np) { /* Fill in a router advert to be sent to my own interface. */ icmp_hdr_t *icmp= (icmp_hdr_t *) (bp->ip + 1); bp->ip->ih_vers_ihl= 0x45; bp->ip->ih_dst= LOCALHOST; icmp->ih_type= ICMP_TYPE_ROUTER_ADVER; icmp->ih_code= 0; icmp->ih_hun.ihh_ram.iram_na= 1; icmp->ih_hun.ihh_ram.iram_aes= 2; icmp->ih_hun.ihh_ram.iram_lt= htons(DELTA_ADV); ((u32_t *) icmp->ih_dun.uhd_data)[0] = np->gateway; ((u32_t *) icmp->ih_dun.uhd_data)[1] = htonl((u32_t) -9999); icmp->ih_chksum= 0; icmp->ih_chksum= ~oneC_sum(0, icmp, 16); } ipaddr_t icmp_is_advert(buf_t *bp) { /* Check if an IP packet is a router advertisement, and if it's genuine, * i.e. the sender is mentioned in the packet. */ icmp_hdr_t *icmp= (icmp_hdr_t *) (bp->ip + 1); int i; if (icmp->ih_type == ICMP_TYPE_ROUTER_ADVER) { for (i= 0; i < icmp->ih_hun.ihh_ram.iram_na; i++) { if (((u32_t *) icmp->ih_dun.uhd_data)[2*i] == bp->ip->ih_src) { /* It's a router! */ return bp->ip->ih_src; } } } return 0; }