From 65f01f92595ea5ff907746a30c62ce08e88c209e Mon Sep 17 00:00:00 2001
From: igutidze <125119026+igutidze@users.noreply.github.com>
Date: Thu, 18 Dec 2025 19:43:43 +0400
Subject: [PATCH 1/4] util.c: log failed attempts to set SO_RCVBUF size

---
 util.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/util.c b/util.c
index 61b36b4..943f923 100644
--- a/util.c
+++ b/util.c
@@ -830,7 +830,11 @@ int OpenSocketSafe( const char *_psz_arg, int i_ttl, uint16_t i_bind_port,
         /* 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 ) );
+        if ( setsockopt( i_fd, SOL_SOCKET, SO_RCVBUF, (void *) &i, sizeof( i ) ) < 0 )
+        {
+            msg_Err( NULL, "couldn't adjust socket receive buffer size (%s)",
+                strerror(errno) );
+        }
 
         /* Join the multicast group if the socket is a multicast address */
         if ( bind_addr.ss.ss_family == AF_INET

From 35571caef8a594c0ee869aea590b4813ae00b85a Mon Sep 17 00:00:00 2001
From: igutidze <125119026+igutidze@users.noreply.github.com>
Date: Thu, 18 Dec 2025 21:10:11 +0400
Subject: [PATCH 2/4] util.c: make sure requested SO_RCVBUF is applied

---
 util.c | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/util.c b/util.c
index 943f923..addf904 100644
--- a/util.c
+++ b/util.c
@@ -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
@@ -827,13 +828,24 @@ 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;
+        /* 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 (%s)",
+            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 */

From 9509ed152f085eeb7f35faca1a264377adf19d8e Mon Sep 17 00:00:00 2001
From: igutidze <125119026+igutidze@users.noreply.github.com>
Date: Thu, 18 Dec 2025 21:13:44 +0400
Subject: [PATCH 3/4] util.c: add rcvbufsz command line option

---
 util.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/util.c b/util.c
index addf904..d7d9e51 100644
--- a/util.c
+++ b/util.c
@@ -682,6 +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 );
 

From 75d14c91156cb6d450eae6467b0a7ff7aec2f5ee Mon Sep 17 00:00:00 2001
From: igutidze <125119026+igutidze@users.noreply.github.com>
Date: Thu, 18 Dec 2025 21:17:09 +0400
Subject: [PATCH 4/4] Update README

---
 README | 1 +
 1 file changed, 1 insertion(+)

diff --git a/README b/README
index e08d7c1..8d71076 100644
--- a/README
+++ b/README
@@ -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