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 GPL version 2, see file LICENSE in this tarball for details.
   8  */
   9
  10 #include "libbb.h"
  11
  12 /*
  13  * This asks kernel to let us know dst addr/port of incoming packets
  14  * We don't check for errors here. Not supported == won't be used
  15  */
  16 void FAST_FUNC
  17 socket_want_pktinfo(int fd)
  18 {
  19 #ifdef IP_PKTINFO
  20         setsockopt(fd, IPPROTO_IP, IP_PKTINFO, &const_int_1, sizeof(int));
  21 #endif
  22 #if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
  23         setsockopt(fd, IPPROTO_IPV6, IPV6_PKTINFO, &const_int_1, sizeof(int));
  24 #endif
  25 }
  26
  27
  28 ssize_t FAST_FUNC
  29 send_to_from(int fd, void *buf, size_t len, int flags,
  30                 const struct sockaddr *to,
  31                 const struct sockaddr *from,
  32                 socklen_t tolen)
  33 {
  34 #ifndef IP_PKTINFO
  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(cbuf...) */
  80                 pktptr->ipi_spec_dst = ((struct sockaddr_in*)from)->sin_addr;
  81         }
  82 #if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
  83         else if (to->sa_family == AF_INET6 && from->sa_family == AF_INET6) {
  84                 struct in6_pktinfo *pktptr;
  85                 cmsgptr->cmsg_level = IPPROTO_IPV6;
  86                 cmsgptr->cmsg_type = IPV6_PKTINFO;
  87                 cmsgptr->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
  88                 pktptr = (struct in6_pktinfo *)(CMSG_DATA(cmsgptr));
  89                 /* pktptr->ipi6_ifindex = 0; -- already done by memset(cbuf...) */
  90                 pktptr->ipi6_addr = ((struct sockaddr_in6*)from)->sin6_addr;
  91         }
  92 #endif
  93         msg.msg_controllen = cmsgptr->cmsg_len;
  94
  95         return sendmsg(fd, &msg, flags);
  96 #endif
  97 }
  98
  99 /* NB: this will never set port# in 'to'!
 100  * _Only_ IP/IPv6 address part of 'to' is _maybe_ modified.
 101  * Typical usage is to preinit 'to' with "default" value
 102  * before calling recv_from_to(). */
 103 ssize_t FAST_FUNC
 104 recv_from_to(int fd, void *buf, size_t len, int flags,
 105                 struct sockaddr *from, struct sockaddr *to,
 106                 socklen_t sa_size)
 107 {
 108 #ifndef IP_PKTINFO
 109         return recvfrom(fd, buf, len, flags, from, &sa_size);
 110 #else
 111         /* man recvmsg and man cmsg is needed to make sense of code below */
 112         struct iovec iov[1];
 113         union {
 114                 char cmsg[CMSG_SPACE(sizeof(struct in_pktinfo))];
 115 #if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
 116                 char cmsg6[CMSG_SPACE(sizeof(struct in6_pktinfo))];
 117 #endif
 118         } u;
 119         struct cmsghdr *cmsgptr;
 120         struct msghdr msg;
 121         ssize_t recv_length;
 122
 123         iov[0].iov_base = buf;
 124         iov[0].iov_len = len;
 125
 126         memset(&msg, 0, sizeof(msg));
 127         msg.msg_name = (struct sockaddr *)from;
 128         msg.msg_namelen = sa_size;
 129         msg.msg_iov = iov;
 130         msg.msg_iovlen = 1;
 131         msg.msg_control = &u;
 132         msg.msg_controllen = sizeof(u);
 133
 134         recv_length = recvmsg(fd, &msg, flags);
 135         if (recv_length < 0)
 136                 return recv_length;
 137
 138         /* Here we try to retrieve destination IP and memorize it */
 139         for (cmsgptr = CMSG_FIRSTHDR(&msg);
 140                         cmsgptr != NULL;
 141                         cmsgptr = CMSG_NXTHDR(&msg, cmsgptr)
 142         ) {
 143                 if (cmsgptr->cmsg_level == IPPROTO_IP
 144                  && cmsgptr->cmsg_type == IP_PKTINFO
 145                 ) {
 146 #define pktinfo(cmsgptr) ( (struct in_pktinfo*)(CMSG_DATA(cmsgptr)) )
 147                         to->sa_family = AF_INET;
 148                         ((struct sockaddr_in*)to)->sin_addr = pktinfo(cmsgptr)->ipi_addr;
 149                         /* ((struct sockaddr_in*)to)->sin_port = 123; */
 150 #undef pktinfo
 151                         break;
 152                 }
 153 #if ENABLE_FEATURE_IPV6 && defined(IPV6_PKTINFO)
 154                 if (cmsgptr->cmsg_level == IPPROTO_IPV6
 155                  && cmsgptr->cmsg_type == IPV6_PKTINFO
 156                 ) {
 157 #define pktinfo(cmsgptr) ( (struct in6_pktinfo*)(CMSG_DATA(cmsgptr)) )
 158                         to->sa_family = AF_INET6;
 159                         ((struct sockaddr_in6*)to)->sin6_addr = pktinfo(cmsgptr)->ipi6_addr;
 160                         /* ((struct sockaddr_in6*)to)->sin6_port = 123; */
 161 #undef pktinfo
 162                         break;
 163                 }
 164 #endif
 165         }
 166         return recv_length;
 167 #endif
 168 }