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

[lance.lmwang@gmail.com]

On Thu, Jan 27, 2022 at 10:30:10AM +0800, "zhilizhao(赵志立)" wrote:
> 
> 
> > On Jan 27, 2022, at 9:59 AM, lance.lmwang@gmail.com wrote:
> > 
> > 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.
> 
> 
> MacOS support int and unsigned char from my test. The upper bound of TTL is limited
> to 255 (limited by protocol design), I guess it’s unrelated to int or unsigned char.

Yes, MacOS isn't caused by one byte or int. By #Ticket9449, it'll failed for ttl=10,
so I guess my proposal which try with one byte again should be work for Openbsd system.
But you can't limit to 255 only as some system support for int like Win32.

> 
> 
> > 
> > #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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> >>> 
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> >>> 
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> >> 
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> > 
> > -- 
> > Thanks,
> > Limin Wang
> > _______________________________________________
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> > ffmpeg-devel@ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > 
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> 
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-- 
Thanks,
Limin Wang
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