commands/dhcpd/ether.c

   1 /*      ether.c - Raw Ethernet stuff
   2  *                                                      Author: Kees J. Bot
   3  *                                                              16 Dec 2000
   4  */
   5 #include <sys/types.h>
   6 #include <fcntl.h>
   7 #include <string.h>
   8 #include <sys/asynchio.h>
   9 #include <net/hton.h>
  10 #include <net/gen/in.h>
  11 #include <net/gen/ether.h>
  12 #include <net/gen/eth_hdr.h>
  13 #include <net/gen/ip_hdr.h>
  14 #include <net/gen/icmp.h>
  15 #include <net/gen/icmp_hdr.h>
  16 #include <net/gen/oneCsum.h>
  17 #include <net/gen/udp.h>
  18 #include <net/gen/udp_hdr.h>
  19 #include <net/gen/dhcp.h>
  20 #include "arp.h"
  21 #include "dhcpd.h"
  22
  23 static ether_addr_t BCAST_ETH = {{ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }};
  24 #define BCAST_IP        HTONL(0xFFFFFFFFUL)
  25 #define LOCALHOST       HTONL(0x7F000001UL)
  26
  27 static u16_t udp_cksum(ipaddr_t src, ipaddr_t dst, udp_hdr_t *udp)
  28 {
  29     /* Compute the checksum of an UDP packet plus data. */
  30     struct udp_pseudo {
  31         ipaddr_t        src, dst;
  32         u8_t            zero, proto;
  33         u16_t           length;
  34     } pseudo;
  35     size_t len;
  36
  37     /* Fill in the UDP pseudo header that must be prefixed to the UDP
  38      * packet to compute the checksum of the whole thing.
  39      */
  40     pseudo.src= src;
  41     pseudo.dst= dst;
  42     pseudo.zero= 0;
  43     pseudo.proto= IPPROTO_UDP;
  44     pseudo.length= udp->uh_length;
  45
  46     len= ntohs(udp->uh_length);
  47     if (len & 1) {
  48         /* Length is odd?  Pad with a zero. */
  49         B(udp)[len++]= 0;
  50     }
  51     return oneC_sum(oneC_sum(0, &pseudo, sizeof(pseudo)), udp, len);
  52 }
  53
  54 void udp2ether(buf_t *bp, network_t *np)
  55 {
  56     /* Transform a packet in UDP format to raw Ethernet.  Ignore the UDP
  57      * addresses, always broadcast from 0.0.0.0.
  58      */
  59     udp_io_hdr_t udpio;
  60
  61     /* Save the UDP I/O header. */
  62     udpio= *bp->udpio;
  63
  64     /* Fill in the Ethernet, IP and UDP headers. */
  65     bp->eth->eh_dst= BCAST_ETH;
  66     bp->eth->eh_src= np->eth;
  67     bp->eth->eh_proto= HTONS(ETH_IP_PROTO);
  68     bp->ip->ih_vers_ihl= 0x45;
  69     bp->ip->ih_tos= 0;
  70     bp->ip->ih_length= htons(sizeof(ip_hdr_t)
  71                         + sizeof(udp_hdr_t) + udpio.uih_data_len);
  72     bp->ip->ih_id= 0;
  73     bp->ip->ih_flags_fragoff= NTOHS(0x4000);
  74     bp->ip->ih_ttl= IP_MAX_TTL;
  75     bp->ip->ih_proto= IPPROTO_UDP;
  76     bp->ip->ih_hdr_chk= 0;
  77     bp->ip->ih_src= 0;
  78     bp->ip->ih_dst= BCAST_IP;
  79     bp->ip->ih_hdr_chk= ~oneC_sum(0, bp->ip, sizeof(*bp->ip));
  80     bp->udp->uh_src_port= udpio.uih_src_port;
  81     bp->udp->uh_dst_port= udpio.uih_dst_port;
  82     bp->udp->uh_length= htons(sizeof(udp_hdr_t) + udpio.uih_data_len);
  83     bp->udp->uh_chksum= 0;
  84     bp->udp->uh_chksum= ~udp_cksum(bp->ip->ih_src, bp->ip->ih_dst, bp->udp);
  85 }
  86
  87 int ether2udp(buf_t *bp)
  88 {
  89     /* Transform an UDP packet read from raw Ethernet to normal UDP.
  90      * Return true iff the packet is indeed UDP and has no errors.
  91      */
  92     udp_io_hdr_t udpio;
  93
  94     if (bp->eth->eh_proto != HTONS(ETH_IP_PROTO)
  95         || bp->ip->ih_vers_ihl != 0x45
  96         || bp->ip->ih_proto != IPPROTO_UDP
  97         || oneC_sum(0, bp->ip, 20) != (u16_t) ~0
  98         || udp_cksum(bp->ip->ih_src, bp->ip->ih_dst, bp->udp) != (u16_t) ~0
  99     ) {
 100         /* Not UDP/IP or checksums bad. */
 101         return 0;
 102     }
 103     udpio.uih_src_addr= bp->ip->ih_src;
 104     udpio.uih_dst_addr= bp->ip->ih_dst;
 105     udpio.uih_src_port= bp->udp->uh_src_port;
 106     udpio.uih_dst_port= bp->udp->uh_dst_port;
 107     udpio.uih_ip_opt_len= 0;
 108     udpio.uih_data_len= ntohs(bp->udp->uh_length) - sizeof(udp_hdr_t);
 109     *bp->udpio= udpio;
 110     return 1;
 111 }
 112
 113 void make_arp(buf_t *bp, network_t *np)
 114 {
 115     /* Create an ARP packet to query for my IP address. */
 116     arp46_t *arp= (arp46_t *) bp->eth;
 117
 118     memset(arp, 0, sizeof(*arp));
 119     arp->dstaddr= BCAST_ETH;
 120     arp->srcaddr= np->eth;
 121     arp->ethtype= HTONS(ETH_ARP_PROTO);
 122     arp->hdr= HTONS(ARP_ETHERNET);
 123     arp->pro= HTONS(ETH_IP_PROTO);
 124     arp->hln= 6;
 125     arp->pln= 4;
 126     arp->op= HTONS(ARP_REQUEST);
 127     arp->sha= np->eth;
 128     memcpy(arp->spa, &np->ip, sizeof(np->ip));
 129     memcpy(arp->tpa, &np->ip, sizeof(np->ip));
 130 }
 131
 132 int is_arp_me(buf_t *bp, network_t *np)
 133 {
 134     /* True iff an ARP packet is a reply from someone else with an address I
 135      * thought was mine.  (That's like, bad.)
 136      */
 137     arp46_t *arp= (arp46_t *) bp->eth;
 138
 139     if (arp->ethtype == HTONS(ETH_ARP_PROTO)
 140         && arp->hdr == HTONS(ARP_ETHERNET)
 141         && arp->pro == HTONS(ETH_IP_PROTO)
 142         && arp->op == HTONS(ARP_REPLY)
 143         && memcmp(&arp->spa, &np->ip, sizeof(np->ip)) == 0
 144         && memcmp(&arp->sha, &np->eth, sizeof(np->eth)) != 0
 145     ) {
 146         np->conflict= arp->sha;
 147         return 1;
 148     }
 149     return 0;
 150 }
 151
 152 void icmp_solicit(buf_t *bp)
 153 {
 154     /* Fill in a router solicitation ICMP packet. */
 155     icmp_hdr_t *icmp= (icmp_hdr_t *) (bp->ip + 1);
 156
 157     bp->ip->ih_vers_ihl= 0x45;
 158     bp->ip->ih_dst= BCAST_IP;
 159
 160     icmp->ih_type= ICMP_TYPE_ROUTE_SOL;
 161     icmp->ih_code= 0;
 162     icmp->ih_hun.ihh_unused= 0;
 163     icmp->ih_chksum= 0;
 164     icmp->ih_chksum= ~oneC_sum(0, icmp, 8);
 165 }
 166
 167 void icmp_advert(buf_t *bp, network_t *np)
 168 {
 169     /* Fill in a router advert to be sent to my own interface. */
 170     icmp_hdr_t *icmp= (icmp_hdr_t *) (bp->ip + 1);
 171
 172     bp->ip->ih_vers_ihl= 0x45;
 173     bp->ip->ih_dst= LOCALHOST;
 174
 175     icmp->ih_type= ICMP_TYPE_ROUTER_ADVER;
 176     icmp->ih_code= 0;
 177     icmp->ih_hun.ihh_ram.iram_na= 1;
 178     icmp->ih_hun.ihh_ram.iram_aes= 2;
 179     icmp->ih_hun.ihh_ram.iram_lt= htons(DELTA_ADV);
 180     ((u32_t *) icmp->ih_dun.uhd_data)[0] = np->gateway;
 181     ((u32_t *) icmp->ih_dun.uhd_data)[1] = HTONL((u32_t) -9999);
 182     icmp->ih_chksum= 0;
 183     icmp->ih_chksum= ~oneC_sum(0, icmp, 16);
 184 }
 185
 186 ipaddr_t icmp_is_advert(buf_t *bp)
 187 {
 188     /* Check if an IP packet is a router advertisement, and if it's genuine,
 189      * i.e. the sender is mentioned in the packet.
 190      */
 191     icmp_hdr_t *icmp= (icmp_hdr_t *) (bp->ip + 1);
 192     int i;
 193
 194     if (icmp->ih_type == ICMP_TYPE_ROUTER_ADVER) {
 195         for (i= 0; i < icmp->ih_hun.ihh_ram.iram_na; i++) {
 196             if (((u32_t *) icmp->ih_dun.uhd_data)[2*i] == bp->ip->ih_src) {
 197                 /* It's a router! */
 198                 return bp->ip->ih_src;
 199             }
 200         }
 201     }
 202     return 0;
 203 }