Re: [FFmpeg-devel] [PATCH] avformat: enable UDP IPv6 multicast interface selection

[epirat07@gmail.com]

On 14 Mar 2024, at 10:22, Ignjatović, Lazar wrote:

> avformat: enable UDP IPv6 multicast interface selection
>
> localaddr option now properly works with IPv6 addresses. Properly resolved
> interface index in places where default 0 interface index is used (marked with
> TODO: within udp.c). Added SO_BINDTODEVICE for mcast sockets that are used for
> reading from the network. Need for this arises from the fact that [ffx1::*] and
> [ffx2::*] mcast addresses need to have a defined interface for binding to avoid
> ambiguity between multiple link-local networks on the same host. Failing to set
> this option causes errors on Linux systems for interface and link-local scopes.
>
> For mcast addresses, bind to mcast address is attempted as before. In case
> that this fails, which will happen on Windows, socket is bound to
> INADDR_ANY/IN6ADDR_ANY_INIT depending on address family. Actual interface
> selection is performed using udp_set_multicast_interface to point to the
> desired interface for sending/listening.
>
> Utilization of sin6_scope_id field enables usage and adequate resolving of
> IPv6 addresses that utilize zone index (e.g. fe80::1ff:fe23:4567:890a%eth2 )
> This is not fully supported on Windows, thus relying on this field is not done
> on Windows systems.
>
> Closes: #368
>
> Signed-off-by: Lazar Ignjatovic <Lazar.Ignjatovic@cubic.com>
> ---
>  configure             |  3 ++
>  libavformat/ip.c      | 45 ++++++++++++++++++++++++
>  libavformat/ip.h      |  6 ++++
>  libavformat/network.h |  6 ++++
>  libavformat/udp.c     | 80 ++++++++++++++++++++++++++++++++++++++-----
>  5 files changed, 132 insertions(+), 8 deletions(-)
>
> diff --git a/configure b/configure
> index c34bdd13f5..77f03948ce 100755
> --- a/configure
> +++ b/configure
> @@ -2256,6 +2256,7 @@ HEADERS_LIST="
>      valgrind_valgrind_h
>      windows_h
>      winsock2_h
> +    iphlpapi_h
>  "
>
>  INTRINSICS_LIST="
> @@ -6408,6 +6409,8 @@ if ! disabled network; then
>          check_struct winsock2.h "struct sockaddr" sa_len
>          check_type ws2tcpip.h "struct sockaddr_in6"
>          check_type ws2tcpip.h "struct sockaddr_storage"
> +        check_headers iphlpapi.h && network_extralibs+=" -liphlpapi" || disable iphlpapi_h
> +        check_func_headers iphlpapi.h GetBestInterfaceEx
>      else
>          disable network
>      fi
> diff --git a/libavformat/ip.c b/libavformat/ip.c
> index b2c7ef07e5..4f2d998c34 100644
> --- a/libavformat/ip.c
> +++ b/libavformat/ip.c
> @@ -18,6 +18,9 @@
>   * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>   */
>
> +#define _DEFAULT_SOURCE
> +#define _SVID_SOURCE
> +
>  #include <string.h>
>  #include "ip.h"
>  #include "libavutil/avstring.h"
> @@ -159,3 +162,45 @@ void ff_ip_reset_filters(IPSourceFilters *filters)
>      filters->nb_include_addrs = 0;
>      filters->nb_exclude_addrs = 0;
>  }
> +
> +unsigned int ff_ip_resolve_interface_index(struct sockaddr_storage *local_addr)
> +{
> +#if HAVE_WINSOCK2_H && HAVE_IPHLPAPI_H
> +    DWORD retval;
> +    unsigned long iface;
> +
> +    if (local_addr == NULL)
> +        return 0;
> +
> +    retval = GetBestInterfaceEx((struct sockaddr*)local_addr, &iface);
> +    if (retval == NO_ERROR)
> +        return iface;
> +
> +    return 0;
> +#elif !HAVE_WINSOCK2_H
> +    struct ifaddrs *ifaddr, *ifa;
> +
> +    if (local_addr == NULL)
> +        return 0;
> +
> +    /* Special case for link-local addresses, relevant interface is stored in sin6_scope_id */
> +#if HAVE_STRUCT_SOCKADDR_IN6 && defined(IN6_IS_ADDR_LINKLOCAL)
> +    if (local_addr->ss_family == AF_INET6 && IN6_IS_ADDR_LINKLOCAL(&((struct sockaddr_in6*)local_addr)->sin6_addr)) {
> +        unsigned int interface;
> +        interface = ((struct sockaddr_in6*)local_addr)->sin6_scope_id;
> +
> +        if (interface != 0)
> +            return interface;
> +    }
> +#endif
> +    if (getifaddrs(&ifaddr) == -1)
> +        return 0;
> +
> +    for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
> +        if (ifa->ifa_addr != NULL && compare_addr((struct sockaddr_storage*)ifa->ifa_addr, local_addr) == 0)
> +            return if_nametoindex(ifa->ifa_name);
> +    }
> +
> +    return 0;
> +#endif
> +}
> diff --git a/libavformat/ip.h b/libavformat/ip.h
> index b76cdab91c..4085e96f08 100644
> --- a/libavformat/ip.h
> +++ b/libavformat/ip.h
> @@ -69,4 +69,10 @@ int ff_ip_parse_blocks(void *log_ctx, const char *buf, IPSourceFilters *filters)
>   */
>  void ff_ip_reset_filters(IPSourceFilters *filters);
>
> +/**
> + * Resolves IP address to an associated interface index
> + * @return interface index, 0 as default interface value on error
> + */
> +unsigned int ff_ip_resolve_interface_index(struct sockaddr_storage *local_addr);
> +
>  #endif /* AVFORMAT_IP_H */
> diff --git a/libavformat/network.h b/libavformat/network.h
> index ca214087fc..2461b651d4 100644
> --- a/libavformat/network.h
> +++ b/libavformat/network.h
> @@ -38,6 +38,10 @@
>  #include <winsock2.h>
>  #include <ws2tcpip.h>
>
> +#if HAVE_IPHLPAPI_H
> +#include <iphlpapi.h>
> +#endif
> +
>  #ifndef EPROTONOSUPPORT
>  #define EPROTONOSUPPORT WSAEPROTONOSUPPORT
>  #endif
> @@ -64,6 +68,8 @@ int ff_neterrno(void);
>  #include <netinet/in.h>
>  #include <netinet/tcp.h>
>  #include <netdb.h>
> +#include <net/if.h>
> +#include <ifaddrs.h>
>
>  #define ff_neterrno() AVERROR(errno)
>  #endif /* HAVE_WINSOCK2_H */
> diff --git a/libavformat/udp.c b/libavformat/udp.c
> index d9514f5026..9b8ca74282 100644
> --- a/libavformat/udp.c
> +++ b/libavformat/udp.c
> @@ -220,8 +220,7 @@ static int udp_join_multicast_group(int sockfd, struct sockaddr *addr,
>          struct ipv6_mreq mreq6;
>
>          memcpy(&mreq6.ipv6mr_multiaddr, &(((struct sockaddr_in6 *)addr)->sin6_addr), sizeof(struct in6_addr));
> -        //TODO: Interface index should be looked up from local_addr
> -        mreq6.ipv6mr_interface = 0;
> +        mreq6.ipv6mr_interface = ff_ip_resolve_interface_index((struct sockaddr_storage *)local_addr);
>          if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &mreq6, sizeof(mreq6)) < 0) {
>              ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IPV6_ADD_MEMBERSHIP)");
>              return ff_neterrno();
> @@ -231,6 +230,38 @@ static int udp_join_multicast_group(int sockfd, struct sockaddr *addr,
>      return 0;
>  }
>
> +static int udp_set_multicast_interface(int sockfd, struct sockaddr *addr,
> +                                    struct sockaddr *local_addr, void *logctx)
> +{
> +#ifdef IP_MULTICAST_IF
> +    if (addr->sa_family == AF_INET) {
> +        struct ip_mreq mreq;
> +
> +        mreq.imr_multiaddr.s_addr = ((struct sockaddr_in *)addr)->sin_addr.s_addr;
> +        if (local_addr)
> +            mreq.imr_interface = ((struct sockaddr_in *)local_addr)->sin_addr;
> +        else
> +            mreq.imr_interface.s_addr = INADDR_ANY;
> +
> +        if (setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_IF, (const void *)&mreq, sizeof(mreq)) < 0) {
> +            ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IP_MULTICAST_IF)");
> +            return ff_neterrno();
> +        }
> +    }
> +#endif
> +#if defined(IPV6_MULTICAST_IF) && defined(IPPROTO_IPV6)
> +    if (addr->sa_family == AF_INET6) {
> +        unsigned int iface = ff_ip_resolve_interface_index((struct sockaddr_storage *)local_addr);
> +
> +        if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_MULTICAST_IF, &iface, sizeof(unsigned int)) < 0) {
> +            ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IPV6_MULTICAST_IF)");
> +            return ff_neterrno();
> +        }
> +    }
> +#endif
> +    return 0;
> +}
> +
>  static int udp_leave_multicast_group(int sockfd, struct sockaddr *addr,
>                                       struct sockaddr *local_addr, void *logctx)
>  {
> @@ -254,8 +285,7 @@ static int udp_leave_multicast_group(int sockfd, struct sockaddr *addr,
>          struct ipv6_mreq mreq6;
>
>          memcpy(&mreq6.ipv6mr_multiaddr, &(((struct sockaddr_in6 *)addr)->sin6_addr), sizeof(struct in6_addr));
> -        //TODO: Interface index should be looked up from local_addr
> -        mreq6.ipv6mr_interface = 0;
> +        mreq6.ipv6mr_interface = ff_ip_resolve_interface_index((struct sockaddr_storage *)local_addr);
>          if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP, &mreq6, sizeof(mreq6)) < 0) {
>              ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IPV6_DROP_MEMBERSHIP)");
>              return -1;
> @@ -282,8 +312,7 @@ static int udp_set_multicast_sources(URLContext *h,
>              struct group_source_req mreqs;
>              int level = addr->sa_family == AF_INET ? IPPROTO_IP : IPPROTO_IPV6;
>
> -            //TODO: Interface index should be looked up from local_addr
> -            mreqs.gsr_interface = 0;
> +            mreqs.gsr_interface = ff_ip_resolve_interface_index(local_addr);
>              memcpy(&mreqs.gsr_group, addr, addr_len);
>              memcpy(&mreqs.gsr_source, &sources[i], sizeof(*sources));
>
> @@ -839,10 +868,39 @@ static int udp_open(URLContext *h, const char *uri, int flags)
>       * port. This fails on windows. This makes sending to the same address
>       * using sendto() fail, so only do it if we're opened in read-only mode. */
>      if (s->is_multicast && (h->flags & AVIO_FLAG_READ)) {
> +#if defined(SO_BINDTODEVICE) && !HAVE_WINSOCK2_H
> +        {
> +            struct ifreq ifr;
> +            unsigned int iface;
> +            iface = ff_ip_resolve_interface_index((struct sockaddr_storage *)&s->local_addr_storage);
> +            memset(&ifr, 0, sizeof(ifr));
> +
> +            if (if_indextoname(iface, ifr.ifr_name)) {
> +                if (setsockopt(udp_fd, SOL_SOCKET, SO_BINDTODEVICE, (void *)&ifr, sizeof(ifr)) < 0) {
> +                    perror("setsockopt SO_BINDTODEVICE");

This should use the proper av_log logging instead.

> +                }
> +            }
> +        }
> +#endif // defined(SO_BINDTODEVICE) && !HAVE_WINSOCK2_H
>          bind_ret = bind(udp_fd,(struct sockaddr *)&s->dest_addr, len);
>      }
> -    /* bind to the local address if not multicast or if the multicast
> -     * bind failed */
> +
> +    /* bind to ADDR_ANY if the multicast bind failed */
> +    if (s->is_multicast && bind_ret < 0) {
> +        struct addrinfo *res;
> +
> +        if (s->dest_addr.ss_family == AF_INET)
> +            res = ff_ip_resolve_host(h, "0.0.0.0", 0, SOCK_DGRAM, AF_UNSPEC, 0);
> +        else if (s->dest_addr.ss_family == AF_INET6)
> +            res = ff_ip_resolve_host(h, "::", 0, SOCK_DGRAM, AF_UNSPEC, 0);
> +
> +        if (res && res->ai_addr) {
> +            bind_ret = bind(udp_fd, res->ai_addr, res->ai_addrlen);
> +        }
> +
> +        freeaddrinfo(res);
> +    }
> +
>      /* the bind is needed to give a port to the socket now */
>      if (bind_ret < 0 && bind(udp_fd,(struct sockaddr *)&my_addr, len) < 0) {
>          ff_log_net_error(h, AV_LOG_ERROR, "bind failed");
> @@ -855,6 +913,12 @@ static int udp_open(URLContext *h, const char *uri, int flags)
>      s->local_port = udp_port(&my_addr, len);
>
>      if (s->is_multicast) {
> +        if ((ret = udp_set_multicast_interface(udp_fd,
> +                                        (struct sockaddr *)&s->dest_addr,
> +                                        (struct sockaddr *)&s->local_addr_storage,
> +                                        h)) < 0)
> +            goto fail;
> +
>          if (h->flags & AVIO_FLAG_WRITE) {
>              /* output */
>              if ((ret = udp_set_multicast_ttl(udp_fd, s->ttl, (struct sockaddr *)&s->dest_addr, h)) < 0)
> --
> 2.41.0.windows.2
>
>
> This message has been marked as Public on 03/14/2024 09:22Z.
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