[FFmpeg-devel] [PATCH v3 2/3] avformat/udp: Fix IP_MULTICAST_TTL for BSD compatibility

[Marton Balint]

On Sat, 5 Feb 2022, lance.lmwang at gmail.com wrote:

> From: Limin Wang <lance.lmwang at gmail.com>
>
> Suggested by zhilizhao, vlc project has solved the compatibility by
> the same way, so I borrowed the comments from vlc project.
>
> Fix #ticket9449
>
> Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> ---
> libavformat/udp.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/libavformat/udp.c b/libavformat/udp.c
> index 8178d0e..1871acf 100644
> --- a/libavformat/udp.c
> +++ b/libavformat/udp.c
> @@ -164,6 +164,10 @@ static int udp_set_multicast_ttl(int sockfd, int mcastTTL,
> {
>     int protocol, cmd;
>
> +    /* There is some confusion in the world whether IP_MULTICAST_TTL
> +     * takes a byte or an int as an argument.
> +     * BSD seems to indicate byte so we are going with that and use
> +     * int and fall back to byte to be safe */
>     switch (addr->sa_family) {
> #ifdef IP_MULTICAST_TTL
>         case AF_INET:
> @@ -182,8 +186,15 @@ static int udp_set_multicast_ttl(int sockfd, int mcastTTL,
>     }
>
>     if (setsockopt(sockfd, protocol, cmd, &mcastTTL, sizeof(mcastTTL)) < 0) {
> -        ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IPV4/IPV6 MULTICAST TTL)");
> -        return ff_neterrno();
> +        /* BSD compatibility */
> +        unsigned char ttl;
> +
> +        ff_log_net_error(logctx, AV_LOG_DEBUG, "setsockopt(IPV4/IPV6 MULTICAST TTL)");
> +        ttl = (unsigned char)(( mcastTTL > 255 ) ? 255 : mcastTTL);

I guess this limit check here is no longer needed after the range 
checking patches, so just remove. Otherwise LGTM.

Thanks,
Marton

> +        if (setsockopt(sockfd, protocol, cmd, &ttl, sizeof(ttl)) < 0) {
> +            ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IPV4/IPV6 MULTICAST TTL)");
> +            return ff_neterrno();
> +        }
>     }
>
>     return 0;
> -- 
> 1.8.3.1
>
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