release/src/router/busybox/libbb/udp_io.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * Utility routines.
   4  *
   5  * Copyright (C) 2007 Denys Vlasenko
   6  *
   7  * Licensed under GPLv2, see file LICENSE in this source tree.
   8  */
   9 #include "libbb.h"
  10
  11 /*
  12  * This asks kernel to let us know dst addr/port of incoming packets
  13  * We don't check for errors here. Not supported == won't be used
  14  */
  15 void FAST_FUNC
  16 socket_want_pktinfo(int fd UNUSED_PARAM)
  17 {
  18 #ifdef IP_PKTINFO
  19         setsockopt(fd, IPPROTO_IP, IP_PKTINFO, &const_int_1, sizeof(int));
  20 #endif
  21 #if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
  22         setsockopt(fd, IPPROTO_IPV6, IPV6_PKTINFO, &const_int_1, sizeof(int));
  23 #endif
  24 }
  25
  26
  27 ssize_t FAST_FUNC
  28 send_to_from(int fd, void *buf, size_t len, int flags,
  29                 const struct sockaddr *to,
  30                 const struct sockaddr *from,
  31                 socklen_t tolen)
  32 {
  33 #ifndef IP_PKTINFO
  34         (void)from; /* suppress "unused from" warning */
  35         return sendto(fd, buf, len, flags, to, tolen);
  36 #else
  37         struct iovec iov[1];
  38         struct msghdr msg;
  39         union {
  40                 char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
  41 # if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
  42                 char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
  43 # endif
  44         } u;
  45         struct cmsghdr* cmsgptr;
  46
  47         if (from->sa_family != AF_INET
  48 # if ENABLE_FEATURE_IPV6
  49          && from->sa_family != AF_INET6
  50 # endif
  51         ) {
  52                 /* ANY local address */
  53                 return sendto(fd, buf, len, flags, to, tolen);
  54         }
  55
  56         /* man recvmsg and man cmsg is needed to make sense of code below */
  57
  58         iov[0].iov_base = buf;
  59         iov[0].iov_len = len;
  60
  61         memset(&u, 0, sizeof(u));
  62
  63         memset(&msg, 0, sizeof(msg));
  64         msg.msg_name = (void *)(struct sockaddr *)to; /* or compiler will annoy us */
  65         msg.msg_namelen = tolen;
  66         msg.msg_iov = iov;
  67         msg.msg_iovlen = 1;
  68         msg.msg_control = &u;
  69         msg.msg_controllen = sizeof(u);
  70         msg.msg_flags = flags;
  71
  72         cmsgptr = CMSG_FIRSTHDR(&msg);
  73         if (to->sa_family == AF_INET && from->sa_family == AF_INET) {
  74                 struct in_pktinfo *pktptr;
  75                 cmsgptr->cmsg_level = IPPROTO_IP;
  76                 cmsgptr->cmsg_type = IP_PKTINFO;
  77                 cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
  78                 pktptr = (struct in_pktinfo *)(CMSG_DATA(cmsgptr));
  79                 /*pktptr->ipi_ifindex = 0; -- already done by memset(u...) */
  80                 /* In general, CMSG_DATA() can be unaligned, but in this case
  81                  * we know for sure it is sufficiently aligned:
  82                  * CMSG_FIRSTHDR simply returns &u above,
  83                  * and CMSG_DATA returns &u + size_t + int + int.
  84                  * Thus direct assignment is ok:
  85                  */
  86                 pktptr->ipi_spec_dst = ((struct sockaddr_in*)from)->sin_addr;
  87         }
  88 # if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
  89         else if (to->sa_family == AF_INET6 && from->sa_family == AF_INET6) {
  90                 struct in6_pktinfo *pktptr;
  91                 cmsgptr->cmsg_level = IPPROTO_IPV6;
  92                 cmsgptr->cmsg_type = IPV6_PKTINFO;
  93                 cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
  94                 pktptr = (struct in6_pktinfo *)(CMSG_DATA(cmsgptr));
  95                 /* pktptr->ipi6_ifindex = 0; -- already done by memset(u...) */
  96                 pktptr->ipi6_addr = ((struct sockaddr_in6*)from)->sin6_addr;
  97         }
  98 # endif
  99         msg.msg_controllen = cmsgptr->cmsg_len;
 100
 101         return sendmsg(fd, &msg, flags);
 102 #endif
 103 }
 104
 105 /* NB: this will never set port# in 'to'!
 106  * _Only_ IP/IPv6 address part of 'to' is _maybe_ modified.
 107  * Typical usage is to preinit 'to' with "default" value
 108  * before calling recv_from_to(). */
 109 ssize_t FAST_FUNC
 110 recv_from_to(int fd, void *buf, size_t len, int flags,
 111                 struct sockaddr *from, struct sockaddr *to,
 112                 socklen_t sa_size)
 113 {
 114 #ifndef IP_PKTINFO
 115         (void)to; /* suppress "unused to" warning */
 116         return recvfrom(fd, buf, len, flags, from, &sa_size);
 117 #else
 118         /* man recvmsg and man cmsg is needed to make sense of code below */
 119         struct iovec iov[1];
 120         union {
 121                 char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
 122 # if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
 123                 char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
 124 # endif
 125         } u;
 126         struct cmsghdr *cmsgptr;
 127         struct msghdr msg;
 128         ssize_t recv_length;
 129
 130         iov[0].iov_base = buf;
 131         iov[0].iov_len = len;
 132
 133         memset(&msg, 0, sizeof(msg));
 134         msg.msg_name = (struct sockaddr *)from;
 135         msg.msg_namelen = sa_size;
 136         msg.msg_iov = iov;
 137         msg.msg_iovlen = 1;
 138         msg.msg_control = &u;
 139         msg.msg_controllen = sizeof(u);
 140
 141         recv_length = recvmsg(fd, &msg, flags);
 142         if (recv_length < 0)
 143                 return recv_length;
 144
 145 # define to4 ((struct sockaddr_in*)to)
 146 # define to6 ((struct sockaddr_in6*)to)
 147         /* Here we try to retrieve destination IP and memorize it */
 148         for (cmsgptr = CMSG_FIRSTHDR(&msg);
 149                         cmsgptr != NULL;
 150                         cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)
 151         ) {
 152                 if (cmsgptr->cmsg_level == IPPROTO_IP
 153                  && cmsgptr->cmsg_type == IP_PKTINFO
 154                 ) {
 155                         const int IPI_ADDR_OFF = offsetof(struct in_pktinfo, ipi_addr);
 156                         to->sa_family = AF_INET;
 157                         /*# define pktinfo(cmsgptr) ( (struct in_pktinfo*)(CMSG_DATA(cmsgptr)) )*/
 158                         /*to4->sin_addr = pktinfo(cmsgptr)->ipi_addr; - may be unaligned */
 159                         memcpy(&to4->sin_addr, (char*)(CMSG_DATA(cmsgptr)) + IPI_ADDR_OFF, sizeof(to4->sin_addr));
 160                         /*to4->sin_port = 123; - this data is not supplied by kernel */
 161                         break;
 162                 }
 163 # if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
 164                 if (cmsgptr->cmsg_level == IPPROTO_IPV6
 165                  && (cmsgptr->cmsg_type == IPV6_PKTINFO
 166 #if defined(IPV6_2292PKTINFO) && defined(IPV6_RECVPKTINFO)
 167                          || cmsgptr->cmsg_type == IPV6_2292PKTINFO
 168 #endif
 169                 )) {
 170                         const int IPI6_ADDR_OFF = offsetof(struct in6_pktinfo, ipi6_addr);
 171                         to->sa_family = AF_INET6;
 172                         /*#  define pktinfo(cmsgptr) ( (struct in6_pktinfo*)(CMSG_DATA(cmsgptr)) )*/
 173                         /*to6->sin6_addr = pktinfo(cmsgptr)->ipi6_addr; - may be unaligned */
 174                         memcpy(&to6->sin6_addr, (char*)(CMSG_DATA(cmsgptr)) + IPI6_ADDR_OFF, sizeof(to6->sin6_addr));
 175                         /*to6->sin6_port = 123; */
 176                         break;
 177                 }
 178 # endif
 179         }
 180         return recv_length;
 181 #endif
 182 }