release/src/router/busybox/networking/udhcp/d6_packet.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Copyright (C) 2011 Denys Vlasenko.
   4  *
   5  * Licensed under GPLv2, see file LICENSE in this source tree.
   6  */
   7 #include "common.h"
   8 #include "d6_common.h"
   9 #include "dhcpd.h"
  10 #include <netinet/in.h>
  11 #include <netinet/if_ether.h>
  12 #include <netpacket/packet.h>
  13
  14 #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
  15 void FAST_FUNC d6_dump_packet(struct d6_packet *packet)
  16 {
  17         if (dhcp_verbose < 2)
  18                 return;
  19
  20         bb_error_msg(
  21                 "xid %x"
  22                 , packet->d6_xid32
  23         );
  24         //*bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
  25         //bb_error_msg(" chaddr %s", buf);
  26 }
  27 #endif
  28
  29 int FAST_FUNC d6_recv_kernel_packet(struct in6_addr *peer_ipv6
  30         UNUSED_PARAM
  31         , struct d6_packet *packet, int fd)
  32 {
  33         int bytes;
  34
  35         memset(packet, 0, sizeof(*packet));
  36         bytes = safe_read(fd, packet, sizeof(*packet));
  37         if (bytes < 0) {
  38                 log1("packet read error, ignoring");
  39                 return bytes; /* returns -1 */
  40         }
  41
  42         if (bytes < offsetof(struct d6_packet, d6_options)) {
  43                 bb_error_msg("packet with bad magic, ignoring");
  44                 return -2;
  45         }
  46         log1("received %s", "a packet");
  47         d6_dump_packet(packet);
  48
  49         return bytes;
  50 }
  51
  52 /* Construct a ipv6+udp header for a packet, send packet */
  53 int FAST_FUNC d6_send_raw_packet(
  54                 struct d6_packet *d6_pkt, unsigned d6_pkt_size,
  55                 struct in6_addr *src_ipv6, int source_port,
  56                 struct in6_addr *dst_ipv6, int dest_port, const uint8_t *dest_arp,
  57                 int ifindex)
  58 {
  59         struct sockaddr_ll dest_sll;
  60         struct ip6_udp_d6_packet packet;
  61         int fd;
  62         int result = -1;
  63         const char *msg;
  64
  65         fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IPV6));
  66         if (fd < 0) {
  67                 msg = "socket(%s)";
  68                 goto ret_msg;
  69         }
  70
  71         memset(&dest_sll, 0, sizeof(dest_sll));
  72         memset(&packet, 0, offsetof(struct ip6_udp_d6_packet, data));
  73         packet.data = *d6_pkt; /* struct copy */
  74
  75         dest_sll.sll_family = AF_PACKET;
  76         dest_sll.sll_protocol = htons(ETH_P_IPV6);
  77         dest_sll.sll_ifindex = ifindex;
  78         dest_sll.sll_halen = 6;
  79         memcpy(dest_sll.sll_addr, dest_arp, 6);
  80
  81         if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) {
  82                 msg = "bind(%s)";
  83                 goto ret_close;
  84         }
  85
  86         packet.ip6.ip6_vfc = (6 << 4); /* 4 bits version, top 4 bits of tclass */
  87         if (src_ipv6)
  88                 packet.ip6.ip6_src = *src_ipv6; /* struct copy */
  89         packet.ip6.ip6_dst = *dst_ipv6; /* struct copy */
  90         packet.udp.source = htons(source_port);
  91         packet.udp.dest = htons(dest_port);
  92         /* size, excluding IP header: */
  93         packet.udp.len = htons(sizeof(struct udphdr) + d6_pkt_size);
  94         packet.ip6.ip6_plen = packet.udp.len;
  95         /*
  96          * Someone was smoking weed (at least) while inventing UDP checksumming:
  97          * UDP checksum skips first four bytes of IPv6 header.
  98          * 'next header' field should be summed as if it is one more byte
  99          * to the right, therefore we write its value (IPPROTO_UDP)
 100          * into ip6_hlim, and its 'real' location remains zero-filled for now.
 101          */
 102         packet.ip6.ip6_hlim = IPPROTO_UDP;
 103         packet.udp.check = inet_cksum(
 104                                 (uint16_t *)&packet + 2,
 105                                 offsetof(struct ip6_udp_d6_packet, data) - 4 + d6_pkt_size
 106         );
 107         /* fix 'hop limit' and 'next header' after UDP checksumming */
 108         packet.ip6.ip6_hlim = 1; /* observed Windows machines to use hlim=1 */
 109         packet.ip6.ip6_nxt = IPPROTO_UDP;
 110
 111         d6_dump_packet(d6_pkt);
 112         result = sendto(fd, &packet, offsetof(struct ip6_udp_d6_packet, data) + d6_pkt_size,
 113                         /*flags:*/ 0,
 114                         (struct sockaddr *) &dest_sll, sizeof(dest_sll)
 115         );
 116         msg = "sendto";
 117  ret_close:
 118         close(fd);
 119         if (result < 0) {
 120  ret_msg:
 121                 bb_perror_msg(msg, "PACKET");
 122         }
 123         return result;
 124 }
 125
 126 /* Let the kernel do all the work for packet generation */
 127 int FAST_FUNC d6_send_kernel_packet(
 128                 struct d6_packet *d6_pkt, unsigned d6_pkt_size,
 129                 struct in6_addr *src_ipv6, int source_port,
 130                 struct in6_addr *dst_ipv6, int dest_port)
 131 {
 132         struct sockaddr_in6 sa;
 133         int fd;
 134         int result = -1;
 135         const char *msg;
 136
 137         fd = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDP);
 138         if (fd < 0) {
 139                 msg = "socket(%s)";
 140                 goto ret_msg;
 141         }
 142         setsockopt_reuseaddr(fd);
 143
 144         memset(&sa, 0, sizeof(sa));
 145         sa.sin6_family = AF_INET6;
 146         sa.sin6_port = htons(source_port);
 147         sa.sin6_addr = *src_ipv6; /* struct copy */
 148         if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
 149                 msg = "bind(%s)";
 150                 goto ret_close;
 151         }
 152
 153         memset(&sa, 0, sizeof(sa));
 154         sa.sin6_family = AF_INET6;
 155         sa.sin6_port = htons(dest_port);
 156         sa.sin6_addr = *dst_ipv6; /* struct copy */
 157         if (connect(fd, (struct sockaddr *)&sa, sizeof(sa)) == -1) {
 158                 msg = "connect";
 159                 goto ret_close;
 160         }
 161
 162         d6_dump_packet(d6_pkt);
 163         result = safe_write(fd, d6_pkt, d6_pkt_size);
 164         msg = "write";
 165  ret_close:
 166         close(fd);
 167         if (result < 0) {
 168  ret_msg:
 169                 bb_perror_msg(msg, "UDP");
 170         }
 171         return result;
 172 }