libinetsocket.c

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#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif

#include "conf.h"
#define LIBSOCKET_VERSION 2.4
#ifdef BD_ANDROID
#define LIBSOCKET_LINUX 0
#else
#define LIBSOCKET_LINUX 1
#endif
#define LIBSOCKET_FREEBSD 0
#define LIBSOCKET_SUNOS 0

#include <errno.h>
#include <net/if.h>
#include <netdb.h>       // getaddrinfo()
#include <netinet/in.h>  // e.g. struct sockaddr_in on OpenBSD
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>  // read()/write()

/*
   The committers of the libsocket project, all rights reserved
   (c) 2012, dermesser <lbo@spheniscida.de>

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:

   1. Redistributions of source code must retain the above copyright notice,
   this list of conditions and the following disclaimer.
   2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

   THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS “AS IS” AND ANY
   EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
   DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
   (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
   (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
   SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

/*
 * Structure of the functions defined here:
 *
 * <Declarations>
 * <Checks on passed arguments>
 * <actual code>
 *
 */

/* Macro definitions */

//# define VERBOSE // Write errors on stderr?

#define LIBSOCKET_BACKLOG \
    128  

// Symbolic macros
#define LIBSOCKET_TCP 1  
#define LIBSOCKET_UDP 2  

#define LIBSOCKET_IPv4 3  
#define LIBSOCKET_IPv6 4  
#define LIBSOCKET_BOTH \
    5  

#define LIBSOCKET_READ 1   
#define LIBSOCKET_WRITE 2  

#define LIBSOCKET_NUMERIC \
    1  


#define debug_write(str)                \
    {                                   \
        int verbose_errno_save = errno; \
        write(2, str, strlen(str));     \
        errno = verbose_errno_save;     \
    }

#ifdef __FreeBSD__
#define _TRADITIONAL_RDNS
#endif

static inline signed int check_error(int return_value) {
#ifdef VERBOSE
    const char *errbuf;
#endif
    if (return_value < 0) {
#ifdef VERBOSE
        errbuf = strerror(errno);
        debug_write(errbuf);
#endif
        return -1;
    }

    return 0;
}

int create_inet_stream_socket(const char *host, const char *service,
                              char proto_osi3, int flags) {
    int sfd, return_value;
    struct addrinfo hint, *result, *result_check;
#ifdef VERBOSE
    const char *errstring;
#endif

    if (host == NULL || service == NULL) return -1;

    memset(&hint, 0, sizeof hint);

    // set address family
    switch (proto_osi3) {
        case LIBSOCKET_IPv4:
            hint.ai_family = AF_INET;
            break;
        case LIBSOCKET_IPv6:
            hint.ai_family = AF_INET6;
            break;
        case LIBSOCKET_BOTH:
            hint.ai_family = AF_UNSPEC;
            break;
        default:
            return -1;
    }

    // Transport protocol is TCP
    hint.ai_socktype = SOCK_STREAM;

    if (0 != (return_value = getaddrinfo(host, service, &hint, &result))) {
#ifdef VERBOSE
        errstring = gai_strerror(return_value);
        debug_write(errstring);
#endif
        return -1;
    }

    // As described in "The Linux Programming Interface", Michael Kerrisk 2010,
    // chapter 59.11 (p. 1220ff)

    for (result_check = result; result_check != NULL;
         result_check = result_check->ai_next)  // go through the linked list of
                                                // struct addrinfo elements
    {
        sfd = socket(result_check->ai_family, result_check->ai_socktype | flags,
                     result_check->ai_protocol);

        if (sfd < 0)  // Error!!!
            continue;

        if (-1 != connect(sfd, result_check->ai_addr,
                          result_check->ai_addrlen))  // connected without error
            break;

        close(sfd);
    }

    // We do now have a working socket STREAM connection to our target

    if (result_check == NULL)  // Have we?
    {
#ifdef VERBOSE
        debug_write(
            "create_inet_stream_socket: Could not connect to any address!\n");
#endif
        int errno_saved = errno;
        close(sfd);
        errno = errno_saved;
        freeaddrinfo(result);
        return -1;
    }
    // Yes :)

    freeaddrinfo(result);

    return sfd;
}

int create_inet_dgram_socket(char proto_osi3, int flags) {
    int sfd;

    if (proto_osi3 != LIBSOCKET_IPv4 && proto_osi3 != LIBSOCKET_IPv6) {
#ifdef VERBOSE
        debug_write(
            "create_inet_dgram_socket: osi3 argument invalid for DGRAM "
            "sockets\n");
#endif
        return -1;
    }

    switch (proto_osi3) {
        case LIBSOCKET_IPv4:
            sfd = socket(AF_INET, SOCK_DGRAM | flags, 0);
            break;
        case LIBSOCKET_IPv6:
            sfd = socket(AF_INET6, SOCK_DGRAM | flags, 0);
            break;
        default:
            return -1;
    }

    if (-1 == check_error(sfd)) return -1;

    return sfd;
}

ssize_t sendto_inet_dgram_socket(int sfd, const void *buf, size_t size,
                                 const char *host, const char *service,
                                 int sendto_flags) {
    struct sockaddr_storage oldsock;
    struct addrinfo *result, *result_check, hint;
    socklen_t oldsocklen = sizeof(struct sockaddr_storage);
    int return_value;
#ifdef VERBOSE
    const char *errstring;
#endif

    if (sfd < 0) return -1;

    if (buf == NULL) return -1;

    if (size == 0) return 0;

    if (host == NULL || service == NULL) return -1;

    if (-1 == check_error(getsockname(sfd, (struct sockaddr *)&oldsock,
                                      (socklen_t *)&oldsocklen)))
        return -1;

    memset(&hint, 0, sizeof(struct addrinfo));

    /*
     * This works for Linux > 2.6.32
        socklen_t dom_len = sizeof(hint.ai_family);
        getsockopt(sfd,SOL_SOCKET,SO_DOMAIN,&hint.ai_family,&dom_len);
    */
    hint.ai_family = oldsock.ss_family;
    hint.ai_socktype = SOCK_DGRAM;

    if (0 != (return_value = getaddrinfo(host, service, &hint, &result))) {
#ifdef VERBOSE
        errstring = gai_strerror(return_value);
        debug_write(errstring);
#endif
        return -1;
    }

    for (result_check = result; result_check != NULL;
         result_check = result_check->ai_next)  // go through the linked list of
                                                // struct addrinfo elements
    {
        if (-1 != (return_value = sendto(
                       sfd, buf, size, sendto_flags, result_check->ai_addr,
                       result_check->ai_addrlen)))  // connected without error
        {
            break;  // Exit loop if send operation was successful
        } else {
            check_error(return_value);
        }
    }

    freeaddrinfo(result);

    return return_value;
}

ssize_t recvfrom_inet_dgram_socket(int sfd, void *buffer, size_t size,
                                   char *src_host, size_t src_host_len,
                                   char *src_service, size_t src_service_len,
                                   int recvfrom_flags, int numeric) {
    struct sockaddr_storage client;

#ifdef _TRADITIONAL_RDNS
    struct sockaddr_storage oldsockaddr;
    socklen_t oldsockaddrlen = sizeof(struct sockaddr_storage);
    struct hostent *he;
    void *addrptr;
    size_t addrlen;
    uint16_t sport = 0;
#endif

    ssize_t bytes;

#ifndef _TRADITIONAL_RDNS
    int retval;
#endif

#ifdef VERBOSE
    const char *errstr;
#endif
    if (sfd < 0) return -1;

    if (buffer == NULL || size == 0)
        return -1;
    else
        memset(buffer, 0, size);

    if (src_host) memset(src_host, 0, src_host_len);
    if (src_service) memset(src_service, 0, src_service_len);

    socklen_t stor_addrlen = sizeof(struct sockaddr_storage);

    if (-1 == check_error(bytes = recvfrom(sfd, buffer, size, recvfrom_flags,
                                           (struct sockaddr *)&client,
                                           &stor_addrlen)))
        return -1;

    if (src_host_len > 0 ||
        src_service_len >
            0)  // If one of the things is wanted. If you give a null pointer
                // with a positive _len parameter, you won't get the address.
    {
        if (numeric == LIBSOCKET_NUMERIC) {
            numeric = NI_NUMERICHOST | NI_NUMERICSERV;
        }

        // getnameinfo() doesn't work on FreeBSD (here)
#ifndef _TRADITIONAL_RDNS
        if (0 !=
            (retval = getnameinfo(
                 (struct sockaddr *)&client, sizeof(struct sockaddr_storage),
                 src_host, src_host_len, src_service, src_service_len,
                 numeric)))  // Write information to the provided memory
        {
#ifdef VERBOSE
            errstr = gai_strerror(retval);
            debug_write(errstr);
#endif
            return -1;
        }
#endif

        // so use traditional methods
#ifdef _TRADITIONAL_RDNS
        if (-1 == check_error(getsockname(sfd, (struct sockaddr *)&oldsockaddr,
                                          &oldsockaddrlen)))
            return -1;

        if (oldsockaddrlen >
            sizeof(struct sockaddr_storage))  // If getsockname truncated the
                                              // struct
            return -1;

        if (oldsockaddr.ss_family == AF_INET) {
            addrptr = &(((struct sockaddr_in *)&client)->sin_addr);
            addrlen = sizeof(struct in_addr);
            sport = ntohs(((struct sockaddr_in *)&client)->sin_port);
        } else if (oldsockaddr.ss_family == AF_INET6) {
            addrptr = &(((struct sockaddr_in6 *)&client)->sin6_addr);
            addrlen = sizeof(struct in6_addr);
            sport = ntohs(((struct sockaddr_in6 *)&client)->sin6_port);
        }

        if (NULL ==
            (he = gethostbyaddr(addrptr, addrlen, oldsockaddr.ss_family))) {
            check_error(-1);
            return -1;
        }

        strncpy(src_host, he->h_name, src_host_len);
        snprintf(src_service, src_service_len, "%u", sport);
#endif
    }

    return bytes;
}

int connect_inet_dgram_socket(int sfd, const char *host, const char *service) {
    struct addrinfo *result, *result_check, hint;
    struct sockaddr_storage oldsockaddr;
    struct sockaddr deconnect;
    socklen_t oldsockaddrlen = sizeof(struct sockaddr_storage);
    int return_value;
#ifdef VERBOSE
    const char *errstring;
#endif

    if (sfd < 0) return -1;

    if (host == NULL) {
        // This does not work on FreeBSD systems. We pretend to disconnect the
        // socket although we don't do so. This is not very severe for the
        // application
#ifndef __FreeBSD__
        memset(&deconnect, 0, sizeof(struct sockaddr));

        deconnect.sa_family = AF_UNSPEC;

        if (check_error(connect(sfd, &deconnect, sizeof(struct sockaddr))))
            return -1;
#endif
        return 0;
    }

    if (-1 == check_error(getsockname(sfd, (struct sockaddr *)&oldsockaddr,
                                      &oldsockaddrlen)))
        return -1;

    if (oldsockaddrlen >
        sizeof(struct sockaddr_storage))  // If getsockname truncated the struct
        return -1;

    memset(&hint, 0, sizeof(struct addrinfo));

    hint.ai_family = ((struct sockaddr_in *)&oldsockaddr)
                         ->sin_family;  // AF_INET or AF_INET6 - offset is same
                                        // at sockaddr_in and sockaddr_in6
    hint.ai_socktype = SOCK_DGRAM;

    if (0 != (return_value = getaddrinfo(host, service, &hint, &result))) {
#ifdef VERBOSE
        errstring = gai_strerror(return_value);
        debug_write(errstring);
#endif
        return -1;
    }

    // As described in "The Linux Programming Interface", Michael Kerrisk 2010,
    // chapter 59.11 (p. 1220ff)

    for (result_check = result; result_check != NULL;
         result_check = result_check->ai_next)  // go through the linked list of
                                                // struct addrinfo elements
    {
        if (-1 != (return_value = connect(
                       sfd, result_check->ai_addr,
                       result_check->ai_addrlen)))  // connected without error
        {
            break;
        } else {
            check_error(return_value);
        }
    }

    // We do now have a working (updated) socket connection to our target

    if (result_check == NULL)  // or not?
    {
#ifdef VERBOSE
        debug_write(
            "connect_inet_dgram_socket: Could not connect to any address!\n");
#endif
        freeaddrinfo(result);
        return -1;
    }

    freeaddrinfo(result);

    return 0;
}

int destroy_inet_socket(int sfd) {
    if (sfd < 0) return -1;

    if (-1 == check_error(close(sfd))) return -1;

    return 0;
}

int shutdown_inet_stream_socket(int sfd, int method) {
    if (sfd < 0) return -1;

    if ((method != LIBSOCKET_READ) && (method != LIBSOCKET_WRITE) &&
        (method != (LIBSOCKET_READ | LIBSOCKET_WRITE)))
        return -1;

    if (method & LIBSOCKET_READ)  // READ is set (0001 && 0001 => 0001 => true)
    {
        if (-1 == check_error(shutdown(sfd, SHUT_RD))) return -1;
    }

    if (method &
        LIBSOCKET_WRITE)  // WRITE is set (0010 && 0010 => 0010 => true)
    {
        if (-1 == check_error(shutdown(sfd, SHUT_WR))) return -1;
    }

    return 0;
}

/*
 * Server part
 *
 */

//                            Bind address         Port TCP/UDP IPv4/6
int create_inet_server_socket(const char *bind_addr, const char *bind_port,
                              char proto_osi4, char proto_osi3, int flags) {
    int sfd, domain, type, retval;
    struct addrinfo *result, *result_check, hints;
#ifdef VERBOSE
    const char *errstr;
#endif

    // if ( flags != SOCK_NONBLOCK && flags != SOCK_CLOEXEC && flags !=
    // (SOCK_CLOEXEC|SOCK_NONBLOCK) && flags != 0 )     return -1;

    if (bind_addr == NULL || bind_port == NULL) return -1;

    switch (proto_osi4) {
        case LIBSOCKET_TCP:
            type = SOCK_STREAM;
            break;
        case LIBSOCKET_UDP:
            type = SOCK_DGRAM;
            break;
        default:
            return -1;
    }
    switch (proto_osi3) {
        case LIBSOCKET_IPv4:
            domain = AF_INET;
            break;
        case LIBSOCKET_IPv6:
            domain = AF_INET6;
            break;
        case LIBSOCKET_BOTH:
            domain = AF_UNSPEC;
            break;
        default:
            return -1;
    }

    memset(&hints, 0, sizeof(struct addrinfo));

    hints.ai_socktype = type;
    hints.ai_family = domain;
    hints.ai_flags = AI_PASSIVE;

    if (0 != (retval = getaddrinfo(bind_addr, bind_port, &hints, &result))) {
#ifdef VERBOSE
        errstr = gai_strerror(retval);
        debug_write(errstr);
#endif
        return -1;
    }

    // As described in "The Linux Programming Interface", Michael Kerrisk 2010,
    // chapter 59.11 (p. 1220ff)
    for (result_check = result; result_check != NULL;
         result_check = result_check->ai_next)  // go through the linked list of
                                                // struct addrinfo elements
    {
        sfd = socket(result_check->ai_family, result_check->ai_socktype | flags,
                     result_check->ai_protocol);

        if (sfd < 0)  // Error at socket()!!!
            continue;

        retval = bind(sfd, result_check->ai_addr,
                      (socklen_t)result_check->ai_addrlen);

        if (retval != 0)  // Error at bind()!!!
        {
            close(sfd);
            continue;
        }

        if (type == LIBSOCKET_TCP) retval = listen(sfd, LIBSOCKET_BACKLOG);

        if (retval == 0)  // If we came until here, there wasn't an error
                          // anywhere. It is safe to cancel the loop here
            break;
        else
            close(sfd);
    }

    if (result_check == NULL) {
#ifdef VERBOSE
        debug_write(
            "create_inet_server_socket: Could not bind to any address!\n");
#endif
        freeaddrinfo(result);
        return -1;
    }

    // We do now have a working socket on which we may call accept()

    freeaddrinfo(result);

    return sfd;
}

//                             Socket    Src string      Src str len Src service
// Src service len         NUMERIC?
int accept_inet_stream_socket(int sfd, char *src_host, size_t src_host_len,
                              char *src_service, size_t src_service_len,
                              int flags, int accept_flags) {
    struct sockaddr_storage client_info;
    int client_sfd;

#ifndef _TRADITIONAL_RDNS
    int retval;
#endif

#ifdef _TRADITIONAL_RDNS
    struct sockaddr_storage oldsockaddr;
    socklen_t oldsockaddrlen = sizeof(struct sockaddr_storage);
    struct hostent *he;
    void *addrptr;
    size_t in_addrlen;
    uint16_t sport = 0;
#endif

#ifdef VERBOSE
    const char *errstr;
#endif
    socklen_t addrlen = sizeof(struct sockaddr_storage);

    // Portable behavior
#if LIBSOCKET_LINUX
    if (-1 ==
        check_error((client_sfd = accept4(sfd, (struct sockaddr *)&client_info,
                                          &addrlen, accept_flags))))  // blocks
        return -1;
#else
    if (-1 ==
        check_error((client_sfd = accept(sfd, (struct sockaddr *)&client_info,
                                         &addrlen))))  // blocks
        return -1;
#endif

    if (src_host_len > 0 ||
        src_service_len >
            0)  // If one of the things is wanted. If you give a null pointer
                // with a positive _len parameter, you won't get the address.
    {
        if (flags == LIBSOCKET_NUMERIC) {
            flags = NI_NUMERICHOST | NI_NUMERICSERV;
        } else {
            flags = 0;  // To prevent errors: Unknown flags are ignored
        }

#ifndef _TRADITIONAL_RDNS
        if (0 != (retval = getnameinfo(
                      (struct sockaddr *)&client_info,
                      sizeof(struct sockaddr_storage), src_host, src_host_len,
                      src_service, src_service_len,
                      flags)))  // Write information to the provided memory
        {
#ifdef VERBOSE
            errstr = gai_strerror(retval);
            debug_write(errstr);
#endif
        }
#endif

#ifdef _TRADITIONAL_RDNS
        if (-1 == check_error(getsockname(sfd, (struct sockaddr *)&oldsockaddr,
                                          &oldsockaddrlen)))
            return -1;

        if (oldsockaddrlen >
            sizeof(struct sockaddr_storage))  // If getsockname truncated the
                                              // struct
            return -1;

        if (oldsockaddr.ss_family == AF_INET) {
            addrptr = &(((struct sockaddr_in *)&client_info)->sin_addr);
            in_addrlen = sizeof(struct in_addr);
            sport = ntohs(((struct sockaddr_in *)&client_info)->sin_port);
        } else if (oldsockaddr.ss_family == AF_INET6) {
            addrptr = &(((struct sockaddr_in6 *)&client_info)->sin6_addr);
            in_addrlen = sizeof(struct in6_addr);
            sport = ntohs(((struct sockaddr_in6 *)&client_info)->sin6_port);
        }

        if (NULL ==
            (he = gethostbyaddr(addrptr, in_addrlen, oldsockaddr.ss_family))) {
            check_error(-1);
            // Don't return with error on name resolution failure
        }

        strncpy(src_host, he->h_name, src_host_len);
        snprintf(src_service, src_service_len, "%u", sport);
#endif
    }

    return client_sfd;
}

int get_address_family(const char *hostname) {
    int return_value;
    struct addrinfo hint, *result;
#ifdef VERBOSE
    const char *errstring;
#endif
    int af;

    if (hostname == NULL) return -1;

    memset(&hint, 0, sizeof hint);

    hint.ai_family = AF_UNSPEC;

    if (0 != (return_value = getaddrinfo(hostname, "0", &hint, &result))) {
#ifdef VERBOSE
        errstring = gai_strerror(return_value);
        debug_write(errstring);
#endif
        return -1;
    }

    if (result == NULL) return -1;

    if (result->ai_family == AF_INET) {
        af = LIBSOCKET_IPv4;
    } else if (result->ai_family == AF_INET6) {
        af = LIBSOCKET_IPv6;
    } else {
        af = -1;
    }

    return af;
}

#ifdef LIBSOCKET_LINUX
int create_multicast_socket(const char *group, const char *port,
                            const char *if_name) {
    int sfd, return_value;
    struct sockaddr maddr, localif;
    struct addrinfo hints, *result;
    struct ip_mreqn mreq4;
    struct ipv6_mreq mreq6;
    struct in_addr any;
    struct ifreq interface;

    memset(&maddr, 0, sizeof(maddr));
    memset(&localif, 0, sizeof(localif));
    memset(&mreq4, 0, sizeof(mreq4));
    memset(&mreq6, 0, sizeof(mreq6));
    memset(&hints, 0, sizeof(hints));
    memset(&interface, 0, sizeof(interface));

    if (-1 == check_error(sfd = create_inet_server_socket(
                              group, port, LIBSOCKET_UDP, LIBSOCKET_BOTH, 0))) {
        return -1;
    }

    hints.ai_socktype = SOCK_DGRAM;
    hints.ai_family = AF_UNSPEC;

    if (0 != (return_value = getaddrinfo(group, port, &hints, &result))) {
        int errno_saved = errno;
#ifdef VERBOSE
        const char *errstring = gai_strerror(return_value);
        debug_write(errstring);
#endif
        close(sfd);
        errno = errno_saved;

        return -1;
    }

    if (result->ai_family == AF_INET) {
        // Result is IPv4 address.
        mreq4.imr_multiaddr = ((struct sockaddr_in *)result->ai_addr)->sin_addr;

        if (if_name == NULL) {
            mreq4.imr_ifindex = 0;
            any.s_addr = INADDR_ANY;
            mreq4.imr_address = any;
        } else {
            memcpy(interface.ifr_name, if_name,
                   strlen(if_name) > IFNAMSIZ ? IFNAMSIZ : strlen(if_name));

            if (-1 == check_error(ioctl(sfd, SIOCGIFINDEX, &interface))) {
                int errno_saved = errno;
                close(sfd);
                errno = errno_saved;
                return -1;
            }

            mreq4.imr_ifindex = interface.ifr_ifindex;
        }

        if (-1 == check_error(setsockopt(sfd, IPPROTO_IP, IP_ADD_MEMBERSHIP,
                                         &mreq4, sizeof(struct ip_mreqn)))) {
            int errno_saved = errno;
            close(sfd);
            errno = errno_saved;
            return -1;
        }
        if (-1 == check_error(setsockopt(sfd, IPPROTO_IP, IP_MULTICAST_IF,
                                         &mreq4, sizeof(struct ip_mreqn)))) {
            int errno_saved = errno;
            close(sfd);
            errno = errno_saved;
            return -1;
        }

        // Setup finished.
        //
    } else if (result->ai_family == AF_INET6) {
        mreq6.ipv6mr_multiaddr =
            ((struct sockaddr_in6 *)result->ai_addr)->sin6_addr;
        mreq6.ipv6mr_interface = 0;

        if (if_name == NULL)
            mreq6.ipv6mr_interface = 0;
        else {
            memcpy(interface.ifr_name, if_name,
                   strlen(if_name) > IFNAMSIZ ? IFNAMSIZ : strlen(if_name));

            if (-1 == check_error(ioctl(sfd, SIOCGIFINDEX, &interface))) {
                int errno_saved = errno;
                close(sfd);
                errno = errno_saved;
                return -1;
            }

            mreq6.ipv6mr_interface = interface.ifr_ifindex;
        }

        if (-1 == check_error(setsockopt(sfd, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP,
                                         &mreq6, sizeof(struct ipv6_mreq)))) {
            int errno_saved = errno;
            close(sfd);
            errno = errno_saved;
            return -1;
        }
        if (-1 == check_error(setsockopt(sfd, IPPROTO_IPV6, IPV6_MULTICAST_IF,
                                         &mreq6.ipv6mr_interface,
                                         sizeof(mreq6.ipv6mr_interface)))) {
            int errno_saved = errno;
            close(sfd);
            errno = errno_saved;
            return -1;
        }
    }

    return sfd;
}

#endif

#undef debug_write