tftpd/recvfrom.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2001-2006 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This program is free software available under the same license
   6  *   as the "OpenBSD" operating system, distributed at
   7  *   http://www.openbsd.org/.
   8  *
   9  * ----------------------------------------------------------------------- */
  10
  11 /*
  12  * recvfrom.c
  13  *
  14  * Emulate recvfrom() using recvmsg(), but try to capture the local address
  15  * since some TFTP clients consider it an error to get the reply from another
  16  * IP address than the request was sent to.
  17  *
  18  */
  19
  20 #include "config.h"             /* Must be included first! */
  21 #include "recvfrom.h"
  22 #include "tftpsubs.h"
  23 #ifdef HAVE_MACHINE_PARAM_H
  24 #include <machine/param.h>      /* Needed on some versions of FreeBSD */
  25 #endif
  26
  27 #if defined(HAVE_RECVMSG) && defined(HAVE_MSGHDR_MSG_CONTROL)
  28
  29 #include <sys/uio.h>
  30
  31 #ifdef IP_PKTINFO
  32 # ifndef HAVE_STRUCT_IN_PKTINFO
  33 #  ifdef __linux__
  34 /* Assume this version of glibc simply lacks the definition */
  35 struct in_pktinfo {
  36   int ipi_ifindex;
  37   struct in_addr ipi_spec_dst;
  38   struct in_addr ipi_addr;
  39 };
  40 #  else
  41 #   undef IP_PKTINFO            /* No definition, no way to get it */
  42 #  endif
  43 # endif
  44 #endif
  45
  46 #ifndef CMSG_LEN
  47 # define CMSG_LEN(size)  (sizeof(struct cmsghdr) + (size))
  48 #endif
  49 #ifndef CMSG_SPACE
  50 # define CMSG_SPACE(size) (sizeof(struct cmsghdr) + (size))
  51 #endif
  52
  53 int
  54 myrecvfrom(int s, void *buf, int len, unsigned int flags,
  55            struct sockaddr *from, int *fromlen,
  56            struct sockaddr_in *myaddr)
  57 {
  58   struct msghdr msg;
  59   struct iovec iov;
  60   int n;
  61   struct cmsghdr *cmptr;
  62   union {
  63     struct cmsghdr cm;
  64 #ifdef IP_PKTINFO
  65     char control[CMSG_SPACE(sizeof(struct in_addr)) +
  66                 CMSG_SPACE(sizeof(struct in_pktinfo))];
  67 #else
  68     char control[CMSG_SPACE(sizeof(struct in_addr))];
  69 #endif
  70   } control_un;
  71   int on = 1;
  72 #ifdef IP_PKTINFO
  73   struct in_pktinfo pktinfo;
  74 #endif
  75
  76   /* Try to enable getting the return address */
  77 #ifdef IP_RECVDSTADDR
  78   setsockopt(s, IPPROTO_IP, IP_RECVDSTADDR, &on, sizeof(on));
  79 #endif
  80 #ifdef IP_PKTINFO
  81   setsockopt(s, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
  82 #endif
  83
  84   bzero(&msg, sizeof msg);      /* Clear possible system-dependent fields */
  85   msg.msg_control = control_un.control;
  86   msg.msg_controllen = sizeof(control_un.control);
  87   msg.msg_flags = 0;
  88
  89   msg.msg_name = from;
  90   msg.msg_namelen = *fromlen;
  91   iov.iov_base = buf;
  92   iov.iov_len  = len;
  93   msg.msg_iov = &iov;
  94   msg.msg_iovlen = 1;
  95
  96   if ( (n = recvmsg(s, &msg, flags)) < 0 )
  97     return n;                   /* Error */
  98
  99   *fromlen = msg.msg_namelen;
 100
 101   if ( myaddr ) {
 102     bzero(myaddr, sizeof(struct sockaddr_in));
 103     myaddr->sin_family = AF_INET;
 104
 105     if ( msg.msg_controllen < sizeof(struct cmsghdr) ||
 106          (msg.msg_flags & MSG_CTRUNC) )
 107       return n;                 /* No information available */
 108
 109     for ( cmptr = CMSG_FIRSTHDR(&msg) ; cmptr != NULL ;
 110           cmptr = CMSG_NXTHDR(&msg, cmptr) ) {
 111
 112 #ifdef IP_RECVDSTADDR
 113       if ( cmptr->cmsg_level == IPPROTO_IP &&
 114            cmptr->cmsg_type == IP_RECVDSTADDR ) {
 115         memcpy(&myaddr->sin_addr, CMSG_DATA(cmptr),
 116                sizeof(struct in_addr));
 117       }
 118 #endif
 119
 120 #ifdef IP_PKTINFO
 121       if ( cmptr->cmsg_level == IPPROTO_IP &&
 122            cmptr->cmsg_type == IP_PKTINFO ) {
 123         memcpy(&pktinfo, CMSG_DATA(cmptr), sizeof(struct in_pktinfo));
 124         memcpy(&myaddr->sin_addr, &pktinfo.ipi_addr, sizeof(struct in_addr));
 125       }
 126 #endif
 127
 128     }
 129   }
 130
 131   return n;
 132 }
 133
 134 #else /* pointless... */
 135
 136 int
 137 myrecvfrom(int s, void *buf, int len, unsigned int flags,
 138            struct sockaddr *from, int *fromlen,
 139            struct sockaddr_in *myaddr)
 140 {
 141   /* There is no way we can get the local address, fudge it */
 142
 143   bzero(myaddr, sizeof(struct sockaddr_in));
 144   myaddr->sin_family = AF_INET;
 145
 146   myaddr->sin_port   = htons(IPPORT_TFTP);
 147   bzero(&myaddr->sin_addr, sizeof(myaddr->sin_addr));
 148
 149   return recvfrom(s,buf,len,flags,from,fromlen);
 150 }
 151
 152 #endif