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Add the ability to control UDP socket receive buffer size via 'rcvbufsz' command-line option #17

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Add the ability to control UDP socket receive buffer size via 'rcvbufsz' command-line option #17

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65f01f9
util.c: log failed attempts to set SO_RCVBUF size
igutidze Dec 18, 2025
35571ca
util.c: make sure requested SO_RCVBUF is applied
igutidze Dec 18, 2025
9509ed1
util.c: add rcvbufsz command line option
igutidze Dec 18, 2025
75d14c9
Update README
igutidze Dec 18, 2025
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1 change: 1 addition & 0 deletions README
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Original file line number Diff line number Diff line change
Expand Up @@ -76,6 +76,7 @@ Options include:
/tcp (binds a TCP socket instead of UDP)
/srcaddr=XXX.XXX.XXX.XXX (source address for raw packets)
/srcportr=XX (source port for raw packets)
/rcvbufsz=XX (UDP receive buffer size)

Example:
239.255.0.1:5004/ttl=64
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26 changes: 22 additions & 4 deletions util.c
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Original file line number Diff line number Diff line change
Expand Up @@ -558,6 +558,7 @@ int OpenSocketSafe( const char *_psz_arg, int i_ttl, uint16_t i_bind_port,
in_addr_t i_raw_srcaddr = INADDR_ANY;
int i_raw_srcport = 0;
char *psz_ifname = NULL;
int i_rcvbufsz = 0x80000;
#ifdef __FreeBSD__
int hincl = 1;
#endif
Expand Down Expand Up @@ -681,6 +682,8 @@ int OpenSocketSafe( const char *_psz_arg, int i_ttl, uint16_t i_bind_port,
i_raw_srcport = strtol( ARG_OPTION("srcport="), NULL, 0 );
else if ( IS_OPTION("fd=") )
i_fd = strtol( ARG_OPTION("fd="), NULL, 0 );
else if ( IS_OPTION("rcvbufsz=") )
i_rcvbufsz = strtol( ARG_OPTION("rcvbufsz="), NULL, 0 );
else
msg_Warn( NULL, "unrecognized option %s", psz_token2 );

Expand Down Expand Up @@ -827,10 +830,25 @@ int OpenSocketSafe( const char *_psz_arg, int i_ttl, uint16_t i_bind_port,

if ( !*pb_tcp )
{
/* Increase the receive buffer size to 1/2MB (8Mb/s during 1/2s) to
* avoid packet loss caused by scheduling problems */
i = 0x80000;
setsockopt( i_fd, SOL_SOCKET, SO_RCVBUF, (void *) &i, sizeof( i ) );
/* Increase the receive buffer size to avoid packet loss caused by scheduling
* problems */
i = i_rcvbufsz;
if ( setsockopt( i_fd, SOL_SOCKET, SO_RCVBUF, (void *) &i, sizeof( i ) ) < 0 )
{
msg_Err( NULL, "couldn't adjust socket receive buffer size to %d (%s)",
i_rcvbufsz, strerror(errno) );
}
size_t len = sizeof(i);
if ( getsockopt( i_fd, SOL_SOCKET, SO_RCVBUF, (void *) &i, (void *) &len ) < 0 )
{
msg_Err( NULL, "couldn't retrieve socket receive buffer size (%s)",
strerror(errno) );
} else {
/* setsockopt doubles requested value, getsockopt returns the doubled value */
if ( i / 2 < i_rcvbufsz )
msg_Err( NULL, "tried to adjust receive buffer to %d but ended up with %d",
i_rcvbufsz, i / 2);
}

/* Join the multicast group if the socket is a multicast address */
if ( bind_addr.ss.ss_family == AF_INET
Expand Down