Re: [FFmpeg-devel] [PATCH] Fix setsockopt IP_MULTICAST_TTL on OpenBSD

[lance.lmwang@gmail.com]

On Wed, Jan 26, 2022 at 09:50:47PM +0100, Marton Balint wrote:
> 
> 
> On Wed, 26 Jan 2022, Brad Smith wrote:
> 
> > On Wed, Jan 12, 2022 at 12:13:14AM -0500, Brad Smith wrote:
> > > Fix setsockopt() usage on OpenBSD with IP_MULTICAST_TTL. The field
> > > type should be an unsigned char on anything but Linux.
> > 
> > Based on feedback so far. Here is a much simpler approach to this issue..
> 
> Win32 needs DWORD unfortunately. I missed it earlier, sorry.
> 
> https://docs.microsoft.com/en-us/windows/win32/winsock/ipproto-ip-socket-options

From my testing on Mac system, it support one byte only, but at least, it'll
report "Invalid argument" only if the ttl > 255. Maybe we can try with one byte
again if the errno is invalid like below. I tested it with ttl > 255 on Mac system
and without "Invalid argument" anymore.

 #ifdef IP_MULTICAST_TTL
+    int ret = 0;
     if (addr->sa_family == AF_INET) {
-        if (setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_TTL, &mcastTTL, sizeof(mcastTTL)) < 0) {
+        ret = setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_TTL, &mcastTTL, sizeof(mcastTTL));
+        /* try with byte also for IP_MULTICAST_TTL for some system like OpenBSD */
+        if (ret < 0 && errno == EINVAL) {
+            unsigned char ttl = mcastTTL;
+            ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IP_MULTICAST_TTL): ");
+            ret = setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl));
+        }
+        if (ret < 0) {
             ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IP_MULTICAST_TTL)");
             return ff_neterrno();


> 
> Regards,
> Marton
> 
> > 
> > 
> > diff --git a/libavformat/udp.c b/libavformat/udp.c
> > index 83c042d079..da1b98890b 100644
> > --- a/libavformat/udp.c
> > +++ b/libavformat/udp.c
> > @@ -164,7 +164,9 @@ static int udp_set_multicast_ttl(int sockfd, int mcastTTL,
> > {
> > #ifdef IP_MULTICAST_TTL
> >     if (addr->sa_family == AF_INET) {
> > -        if (setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_TTL, &mcastTTL, sizeof(mcastTTL)) < 0) {
> > +        unsigned char ttl = mcastTTL;  /* ignore the outdated Linux documentation */
> > +
> > +        if (setsockopt(sockfd, IPPROTO_IP, IP_MULTICAST_TTL, &ttl, sizeof(ttl)) < 0) {
> >             ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IP_MULTICAST_TTL)");
> >             return ff_neterrno();
> >         }
> > _______________________________________________
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> > ffmpeg-devel@ffmpeg.org
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> > 
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> > 
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-- 
Thanks,
Limin Wang
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