udpfromto.c

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/*
 *   This library is free software; you can redistribute it and/or
 *   modify it under the terms of the GNU Lesser General Public
 *   License as published by the Free Software Foundation; either
 *   version 2.1 of the License, or (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 *   Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public
 *   License along with this library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */

/**
 * $Id: 8f7152471c399ae11ad198d33229e1ff934e6131 $
 * @file udpfromto.c
 * @brief Like recvfrom, but also stores the destination IP address. Useful on multihomed hosts.
 *
 * @copyright 2007 Alan DeKok <aland@deployingradius.com>
 * @copyright 2002 Miquel van Smoorenburg
 */
RCSID("$Id: 8f7152471c399ae11ad198d33229e1ff934e6131 $")

#include <freeradius-devel/udpfromto.h>

#ifdef WITH_UDPFROMTO

#ifdef HAVE_SYS_UIO_H
#  include <sys/uio.h>
#endif

#include <fcntl.h>

/*
 *      More portability idiocy
 *      Mac OSX Lion doesn't define SOL_IP.  But IPPROTO_IP works.
 */
#ifndef SOL_IP
#  define SOL_IP IPPROTO_IP
#endif

/*
 *  glibc 2.4 and uClibc 0.9.29 introduce IPV6_RECVPKTINFO etc. and
 *  change IPV6_PKTINFO This is only supported in Linux kernel >=
 *  2.6.14
 *
 *  This is only an approximation because the kernel version that libc
 *  was compiled against could be older or newer than the one being
 *  run.  But this should not be a problem -- we just keep using the
 *  old kernel interface.
 */
#ifdef __linux__
#  ifdef IPV6_RECVPKTINFO
#    include <linux/version.h>
#    if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,14)
#      ifdef IPV6_2292PKTINFO
#        undef IPV6_RECVPKTINFO
#        undef IPV6_PKTINFO
#        define IPV6_RECVPKTINFO IPV6_2292PKTINFO
#        define IPV6_PKTINFO IPV6_2292PKTINFO
#      endif
#    endif
/* Fall back to the legacy socket option if IPV6_RECVPKTINFO isn't defined */
#  elif defined(IPV6_2292PKTINFO)
#      define IPV6_RECVPKTINFO IPV6_2292PKTINFO
#  endif
#else

/*
 *  For everything that's not Linux we assume RFC 3542 compliance
 *  - setsockopt() takes IPV6_RECVPKTINFO
 *  - cmsg_type is IPV6_PKTINFO (in sendmsg, recvmsg)
 *
 *  If we don't have IPV6_RECVPKTINFO defined but do have IPV6_PKTINFO
 *  defined, chances are the API is RFC2292 compliant and we need to use
 *  IPV6_PKTINFO for both.
 */
#  if !defined(IPV6_RECVPKTINFO) && defined(IPV6_PKTINFO)
#    define IPV6_RECVPKTINFO IPV6_PKTINFO

/*
 *  Ensure IPV6_RECVPKTINFO is not defined somehow if we have we
 *  don't have IPV6_PKTINFO.
 */
#  elif !defined(IPV6_PKTINFO)
#    undef IPV6_RECVPKTINFO
#  endif
#endif

int udpfromto_init(int s)
{
        int proto, flag = 0, opt = 1;
        struct sockaddr_storage si;
        socklen_t si_len = sizeof(si);

        errno = ENOSYS;

        /*
         *      Clang analyzer doesn't see that getsockname initialises
         *      the memory passed to it.
         */
#ifdef __clang_analyzer__
        memset(&si, 0, sizeof(si));
#endif

        if (getsockname(s, (struct sockaddr *) &si, &si_len) < 0) {
                return -1;
        }

        if (si.ss_family == AF_INET) {
#ifdef HAVE_IP_PKTINFO
                /*
                 *      Linux
                 */
                proto = SOL_IP;
                flag = IP_PKTINFO;
#else
#  ifdef IP_RECVDSTADDR

                /*
                 *      Set the IP_RECVDSTADDR option (BSD).  Note:
                 *      IP_RECVDSTADDR == IP_SENDSRCADDR
                 */
                proto = IPPROTO_IP;
                flag = IP_RECVDSTADDR;
#  else
                return -1;
#  endif
#endif

#if defined(AF_INET6) && defined(IPV6_PKTINFO)
        } else if (si.ss_family == AF_INET6) {
                /*
                 *      This should actually be standard IPv6
                 */
                proto = IPPROTO_IPV6;

                /*
                 *      Work around Linux-specific hackery.
                 */
                flag = IPV6_RECVPKTINFO;
        } else {
#endif

                /*
                 *      Unknown AF.  Return an error if possible.
                 */
#  ifdef EPROTONOSUPPORT
                errno = EPROTONOSUPPORT;
#  endif
                return -1;
        }

        return setsockopt(s, proto, flag, &opt, sizeof(opt));
}

/** Read a packet from a file descriptor, retrieving additional header information
 *
 * Abstracts away the complexity of using the complexity of using recvmsg().
 *
 * In addition to reading data from the file descriptor, the src and dst addresses
 * and the receiving interface index are retrieved.  This enables us to send
 * replies using the correct IP interface, in the case where the server is multihomed.
 * This is not normally possible on unconnected datagram sockets.
 *
 * @param[in] s The file descriptor to read from.
 * @param[out] buf Where to write the received datagram data.
 * @param[in] len of buf.
 * @param[in] flags passed unmolested to recvmsg.
 * @param[out] from Where to write the source address.
 * @param[in] fromlen Length of the structure pointed to by from.
 * @param[out] to Where to write the destination address.  If NULL recvmsg() will be used instead.
 * @param[in] tolen Length of the structure pointed to by to.
 * @param[out] if_index The interface which received the datagram (may be NULL).  Will only be
 *      populated if to is not NULL.
 * @param[out] when the packet was received (may be NULL).  If SO_TIMESTAMP is not available
 *      or SO_TIMESTAMP Was not set on the socket, gettimeofday will be used instead.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int recvfromto(int s, void *buf, size_t len, int flags,
               struct sockaddr *from, socklen_t *fromlen,
               struct sockaddr *to, socklen_t *tolen,
               int *if_index, struct timeval *when)
{
        struct msghdr msgh;
        struct cmsghdr *cmsg;
        struct iovec iov;
        char cbuf[256];
        int err;
        struct sockaddr_storage si;
        socklen_t si_len = sizeof(si);

#if !defined(IP_PKTINFO) && !defined(IP_RECVDSTADDR) && !defined(IPV6_PKTINFO)
        /*
         *      If the recvmsg() flags aren't defined, fall back to
         *      using recvfrom().
         */
        to = NULL:
#endif

        /*
         *      Catch the case where the caller passes invalid arguments.
         */
        if (!to || !tolen) {
                if (when) gettimeofday(when, NULL);
                return recvfrom(s, buf, len, flags, from, fromlen);
        }

        /*
         *      Clang analyzer doesn't see that getsockname initialises
         *      the memory passed to it.
         */
#ifdef __clang_analyzer__
        memset(&si, 0, sizeof(si));
#endif

        /*
         *      recvmsg doesn't provide sin_port so we have to
         *      retrieve it using getsockname().
         */
        if (getsockname(s, (struct sockaddr *)&si, &si_len) < 0) {
                return -1;
        }

        /*
         *      Initialize the 'to' address.  It may be INADDR_ANY here,
         *      with a more specific address given by recvmsg(), below.
         */
        if (si.ss_family == AF_INET) {
#if !defined(IP_PKTINFO) && !defined(IP_RECVDSTADDR)
                return recvfrom(s, buf, len, flags, from, fromlen);
#else
                struct sockaddr_in *dst = (struct sockaddr_in *) to;
                struct sockaddr_in *src = (struct sockaddr_in *) &si;

                if (*tolen < sizeof(*dst)) {
                        errno = EINVAL;
                        return -1;
                }
                *tolen = sizeof(*dst);
                *dst = *src;
#endif
        }

#ifdef AF_INET6
        else if (si.ss_family == AF_INET6) {
#if !defined(IPV6_PKTINFO)
                return recvfrom(s, buf, len, flags, from, fromlen);
#else
                struct sockaddr_in6 *dst = (struct sockaddr_in6 *) to;
                struct sockaddr_in6 *src = (struct sockaddr_in6 *) &si;

                if (*tolen < sizeof(*dst)) {
                        errno = EINVAL;
                        return -1;
                }
                *tolen = sizeof(*dst);
                *dst = *src;
#endif
        }
#endif
        /*
         *      Unknown address family.
         */
        else {
                errno = EINVAL;
                return -1;
        }

        /* Set up iov and msgh structures. */
        memset(&cbuf, 0, sizeof(cbuf));
        memset(&msgh, 0, sizeof(struct msghdr));
        iov.iov_base = buf;
        iov.iov_len  = len;
        msgh.msg_control = cbuf;
        msgh.msg_controllen = sizeof(cbuf);
        msgh.msg_name = from;
        msgh.msg_namelen = fromlen ? *fromlen : 0;
        msgh.msg_iov  = &iov;
        msgh.msg_iovlen = 1;
        msgh.msg_flags = 0;

        /* Receive one packet. */
        if ((err = recvmsg(s, &msgh, flags)) < 0) {
                return err;
        }

        if (fromlen) *fromlen = msgh.msg_namelen;

        if (if_index) *if_index = 0;
        if (when) {
                when->tv_sec = 0;
                when->tv_usec = 0;
        }

        /* Process auxiliary received data in msgh */
        for (cmsg = CMSG_FIRSTHDR(&msgh);
             cmsg != NULL;
             cmsg = CMSG_NXTHDR(&msgh,cmsg)) {

#ifdef IP_PKTINFO
                if ((cmsg->cmsg_level == SOL_IP) &&
                    (cmsg->cmsg_type == IP_PKTINFO)) {
                        struct in_pktinfo *i = (struct in_pktinfo *) CMSG_DATA(cmsg);
                        ((struct sockaddr_in *)to)->sin_addr = i->ipi_addr;
                        *tolen = sizeof(struct sockaddr_in);
                        if (if_index) *if_index = i->ipi_ifindex;
                        break;
                }
#endif

#ifdef IP_RECVDSTADDR
                if ((cmsg->cmsg_level == IPPROTO_IP) &&
                    (cmsg->cmsg_type == IP_RECVDSTADDR)) {
                        struct in_addr *i = (struct in_addr *) CMSG_DATA(cmsg);
                        ((struct sockaddr_in *)to)->sin_addr = *i;
                        *tolen = sizeof(struct sockaddr_in);
                        break;
                }
#endif

#ifdef IPV6_PKTINFO
                if ((cmsg->cmsg_level == IPPROTO_IPV6) &&
                    (cmsg->cmsg_type == IPV6_PKTINFO)) {
                        struct in6_pktinfo *i =
                                (struct in6_pktinfo *) CMSG_DATA(cmsg);
                        ((struct sockaddr_in6 *)to)->sin6_addr = i->ipi6_addr;
                        *tolen = sizeof(struct sockaddr_in6);
                        if (if_index) *if_index = i->ipi6_ifindex;
                        break;
                }
#endif

#ifdef SO_TIMESTAMP
                if (when && (cmsg->cmsg_level == SOL_IP) &&
                    (cmsg->cmsg_type == SO_TIMESTAMP)) {
                        memcpy(when, CMSG_DATA(cmsg), sizeof(*when));
                }
#endif
        }

        if (when && !when->tv_sec) gettimeofday(when, NULL);

        return err;
}

/** Send packet via a file descriptor, setting the src address and outbound interface
 *
 * Abstracts away the complexity of using the complexity of using sendmsg().
 *
 * @param[in] s The file descriptor to write to.
 * @param[out] buf Where to read datagram data.
 * @param[in] len of datagram data.
 * @param[in] flags passed unmolested to sendmsg.
 * @param[out] from The source address.
 * @param[in] fromlen Length of the structure pointed to by from.
 * @param[out] to The destination address.
 * @param[in] tolen Length of the structure pointed to by to.
 * @param[out] if_index The interface on which to send the datagram.  Only used if to
 *      is not NULL.  If automatic interface selection is desired, value should be 0.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int sendfromto(int s, void *buf, size_t len, int flags,
               struct sockaddr *from, socklen_t fromlen,
               struct sockaddr *to, socklen_t tolen, int if_index)
{
        struct msghdr msgh;
        struct iovec iov;
        char cbuf[256];

        /*
         *      Unknown address family, die.
         */
        if (from && (from->sa_family != AF_INET) && (from->sa_family != AF_INET6)) {
                errno = EINVAL;
                return -1;
        }

#ifdef __FreeBSD__
        /*
         *      FreeBSD is extra pedantic about the use of IP_SENDSRCADDR,
         *      and sendmsg will fail with EINVAL if IP_SENDSRCADDR is used
         *      with a socket which is bound to something other than
         *      INADDR_ANY
         */
        struct sockaddr bound;
        socklen_t bound_len = sizeof(bound);

        if (getsockname(s, &bound, &bound_len) < 0) {
                return -1;
        }

        switch (bound.sa_family) {
        case AF_INET:
                if (((struct sockaddr_in *) &bound)->sin_addr.s_addr != INADDR_ANY) {
                        from = NULL;
                }
                break;

        case AF_INET6:
                if (!IN6_IS_ADDR_UNSPECIFIED(&((struct sockaddr_in6 *) &bound)->sin6_addr)) {
                        from = NULL;
                }
                break;
        }
#endif  /* !__FreeBSD__ */

        /*
         *      If the sendmsg() flags aren't defined, fall back to
         *      using sendto().  These flags are defined on FreeBSD,
         *      but laying it out this way simplifies the look of the
         *      code.
         */
#  if !defined(IP_PKTINFO) && !defined(IP_SENDSRCADDR)
        if (from && from->sa_family == AF_INET) {
                from = NULL;
        }
#  endif

#  if !defined(IPV6_PKTINFO)
        if (from && from->sa_family == AF_INET6) {
                from = NULL;
        }
#  endif

        /*
         *      No "from", just use regular sendto.
         */
        if (!from || (fromlen == 0)) {
                return sendto(s, buf, len, flags, to, tolen);
        }

        /* Set up control buffer iov and msgh structures. */
        memset(&cbuf, 0, sizeof(cbuf));
        memset(&msgh, 0, sizeof(msgh));
        memset(&iov, 0, sizeof(iov));
        iov.iov_base = buf;
        iov.iov_len = len;

        msgh.msg_iov = &iov;
        msgh.msg_iovlen = 1;
        msgh.msg_name = to;
        msgh.msg_namelen = tolen;

# if defined(IP_PKTINFO) || defined(IP_SENDSRCADDR)
        if (from->sa_family == AF_INET) {
                struct sockaddr_in *s4 = (struct sockaddr_in *) from;

#  ifdef IP_PKTINFO
                struct cmsghdr *cmsg;
                struct in_pktinfo *pkt;

                msgh.msg_control = cbuf;
                msgh.msg_controllen = CMSG_SPACE(sizeof(*pkt));

                cmsg = CMSG_FIRSTHDR(&msgh);
                cmsg->cmsg_level = SOL_IP;
                cmsg->cmsg_type = IP_PKTINFO;
                cmsg->cmsg_len = CMSG_LEN(sizeof(*pkt));

                pkt = (struct in_pktinfo *) CMSG_DATA(cmsg);
                memset(pkt, 0, sizeof(*pkt));
                pkt->ipi_spec_dst = s4->sin_addr;
                pkt->ipi_ifindex = if_index;
#  endif

#  ifdef IP_SENDSRCADDR
                struct cmsghdr *cmsg;
                struct in_addr *in;

                msgh.msg_control = cbuf;
                msgh.msg_controllen = CMSG_SPACE(sizeof(*in));

                cmsg = CMSG_FIRSTHDR(&msgh);
                cmsg->cmsg_level = IPPROTO_IP;
                cmsg->cmsg_type = IP_SENDSRCADDR;
                cmsg->cmsg_len = CMSG_LEN(sizeof(*in));

                in = (struct in_addr *) CMSG_DATA(cmsg);
                *in = s4->sin_addr;
#  endif
        }
#endif

#  if defined(IPV6_PKTINFO)
        if (from->sa_family == AF_INET6) {
                struct sockaddr_in6 *s6 = (struct sockaddr_in6 *) from;

                struct cmsghdr *cmsg;
                struct in6_pktinfo *pkt;

                msgh.msg_control = cbuf;
                msgh.msg_controllen = CMSG_SPACE(sizeof(*pkt));

                cmsg = CMSG_FIRSTHDR(&msgh);
                cmsg->cmsg_level = IPPROTO_IPV6;
                cmsg->cmsg_type = IPV6_PKTINFO;
                cmsg->cmsg_len = CMSG_LEN(sizeof(*pkt));

                pkt = (struct in6_pktinfo *) CMSG_DATA(cmsg);
                memset(pkt, 0, sizeof(*pkt));
                pkt->ipi6_addr = s6->sin6_addr;
                pkt->ipi6_ifindex = if_index;
        }
#  endif        /* IPV6_PKTINFO */

        return sendmsg(s, &msgh, flags);
}


#ifdef TESTING
/*
 *      Small test program to test recvfromto/sendfromto
 *
 *      use a virtual IP address as first argument to test
 *
 *      reply packet should originate from virtual IP and not
 *      from the default interface the alias is bound to
 */
#  include <sys/wait.h>

#  define DEF_PORT 20000                /* default port to listen on */
#  define DESTIP "127.0.0.1"    /* send packet to localhost per default */
#  define TESTSTRING "foo"      /* what to send */
#  define TESTLEN 4                     /* 4 bytes */

int main(int argc, char **argv)
{
        struct sockaddr_in from, to, in;
        char buf[TESTLEN];
        char *destip = DESTIP;
        uint16_t port = DEF_PORT;
        int n, server_socket, client_socket, fl, tl, pid;
        int if_index;
        struct timeval when;

        if (argc > 1) destip = argv[1];
        if (argc > 2) port = atoi(argv[2]);

        in.sin_family = AF_INET;
        in.sin_addr.s_addr = INADDR_ANY;
        in.sin_port = htons(port);
        fl = tl = sizeof(struct sockaddr_in);
        memset(&from, 0, sizeof(from));
        memset(&to,   0, sizeof(to));

        switch (pid = fork()) {
                case -1:
                        perror("fork");
                        return 0;
                case 0:
                        /* child */
                        usleep(100000);
                        goto client;
        }

        /* parent: server */
        server_socket = socket(PF_INET, SOCK_DGRAM, 0);
        if (udpfromto_init(server_socket) != 0) {
                perror("udpfromto_init\n");
                waitpid(pid, NULL, WNOHANG);
                return 0;
        }

        if (bind(server_socket, (struct sockaddr *)&in, sizeof(in)) < 0) {
                perror("server: bind");
                waitpid(pid, NULL, WNOHANG);
                return 0;
        }

        printf("server: waiting for packets on INADDR_ANY:%d\n", port);
        if ((n = recvfromto(server_socket, buf, sizeof(buf), 0,
            (struct sockaddr *)&from, &fl,
            (struct sockaddr *)&to, &tl, &if_index, &when)) < 0) {
                perror("server: recvfromto");
                waitpid(pid, NULL, WNOHANG);
                return 0;
        }

        printf("server: received a packet of %d bytes [%s] ", n, buf);
        printf("(src ip:port %s:%d ",
                inet_ntoa(from.sin_addr), ntohs(from.sin_port));
        printf(" dst ip:port %s:%d) via if %i\n",
                inet_ntoa(to.sin_addr), ntohs(to.sin_port), if_index);

        printf("server: replying from address packet was received on to source address\n");

        if ((n = sendfromto(server_socket, buf, n, 0,
                (struct sockaddr *)&to, tl,
                (struct sockaddr *)&from, fl, 0)) < 0) {
                perror("server: sendfromto");
        }

        waitpid(pid, NULL, 0);
        return 0;

client:
        close(server_socket);
        client_socket = socket(PF_INET, SOCK_DGRAM, 0);
        if (udpfromto_init(client_socket) != 0) {
                perror("udpfromto_init");
                fr_exit_now(0);
        }
        /* bind client on different port */
        in.sin_port = htons(port+1);
        if (bind(client_socket, (struct sockaddr *)&in, sizeof(in)) < 0) {
                perror("client: bind");
                fr_exit_now(0);
        }

        in.sin_port = htons(port);
        in.sin_addr.s_addr = inet_addr(destip);

        printf("client: sending packet to %s:%d\n", destip, port);
        if (sendto(client_socket, TESTSTRING, TESTLEN, 0,
                        (struct sockaddr *)&in, sizeof(in)) < 0) {
                perror("client: sendto");
                fr_exit_now(0);
        }

        printf("client: waiting for reply from server on INADDR_ANY:%d\n", port+1);

        if ((n = recvfromto(client_socket, buf, sizeof(buf), 0,
                            (struct sockaddr *)&from, &fl,
                            (struct sockaddr *)&to, &tl, &if_index)) < 0) {
                perror("client: recvfromto");
                fr_exit_now(0);
        }

        printf("client: received a packet of %d bytes [%s] ", n, buf);
        printf("(src ip:port %s:%d",
                inet_ntoa(from.sin_addr), ntohs(from.sin_port));
        printf(" dst ip:port %s:%d) via if %i\n",
                inet_ntoa(to.sin_addr), ntohs(to.sin_port), if_index);

        fr_exit_now(0);
}

#endif /* TESTING */
#endif /* WITH_UDPFROMTO */