UDP-LISTEN would alway set SO_REUSEADDR even without fork option and when user set it to 0

CHANGES

@@ -38,6 +38,9 @@ corrections:
 	socket using address GOPEN. Thanks to Martin Forssen for bug report and
 	patch.
  
+	UDP-LISTEN would alway set SO_REUSEADDR even without fork option and
+	when user set it to 0. Thanks to Michal Svoboda for reporting this bug.
+
 	docu mentions option so-bindtodev but correct name is so-bindtodevice. 
 	Thanks to Jim Zimmerman for reporting.
 

test.sh

@@ -6115,6 +6115,63 @@ esac
 N=$((N+1))
 
 
+NAME=UDPLISTENFORK
+case "$TESTS" in
+*%functions%*|*%ip4%*|*%udp%*|*%listen%*|*%fork%*|*%$NAME%*)
+TEST="$NAME: UDP socket rebinds after first connection"
+if ! eval $NUMCOND; then :; else
+tf="$td/test$N.stdout"
+te="$td/test$N.stderr"
+tdiff="$td/test$N.diff"
+da1="test$N $(date) $RANDOM"
+da2="test$N $(date) $RANDOM"
+#establish a listening and forking udp socket in background
+SRV="$SOCAT $opts -lpserver UDP4-LISTEN:$PORT,bind=$LOCALHOST,fork PIPE"
+#make a first and a second connection
+CLI="$SOCAT $opts -lpclient - UDP4-CONNECT:$LOCALHOST:$PORT"
+$PRINTF "test $F_n $TEST... " $N
+eval "$SRV 2>${te}s &"
+pids=$!
+waitudp4port "$PORT"
+echo "$da1" |eval "$CLI" >"${tf}1" 2>"${te}1"
+if [ $? -ne 0 ]; then
+    kill "$pids" 2>/dev/null
+    $PRINTF "$NO_RESULT (first conn failed):\n"
+    echo "$SRV &"
+    echo "$CLI"
+    cat "${te}s" "${te}1"
+    numCANT=$((numCANT+1))
+elif ! echo "$da1" |diff - "${tf}1" >"$tdiff"; then
+    kill "$pids" 2>/dev/null
+    $PRINTF "$NO_RESULT (first conn failed); diff:\n"
+    cat "$tdiff"
+    numCANT=$((numCANT+1))
+else
+sleep 2                # UDP-LISTEN sleeps 1s
+echo "$da2" |eval "$CLI" >"${tf}2" 2>"${te}2"
+rc="$?"; kill "$pids" 2>/dev/null
+if [ $rc -ne 0 ]; then
+    $PRINTF "$FAILED:\n"
+    echo "$SRV &"
+    echo "$CLI"
+    cat "${te}s" "${te}2"
+    numFAIL=$((numFAIL+1))
+elif ! echo "$da2" |diff - "${tf}2" >"$tdiff"; then
+    $PRINTF "$FAILED: diff\n"
+    cat "$tdiff"
+    numFAIL=$((numFAIL+1))
+else
+    $PRINTF "$OK\n"
+    numOK=$((numOK+1))
+fi # !( $? -ne 0)
+fi # !(rc -ne 0)
+wait
+fi ;; # NUMCOND, feats
+esac
+PORT=$((PORT+1))
+N=$((N+1))
+
+
 NAME=UNIXLISTENFORK
 case "$TESTS" in
 *%functions%*|*%unix%*|*%listen%*|*%fork%*|*%$NAME%*)
@@ -10786,6 +10843,7 @@ esac
 N=$((N+1))
 
 
+
 # socat up to 1.7.2.0 and  2.0.0-b4 had a bug in xioscan_readline() that could
 # be exploited 
 # to overflow a heap based buffer (socat security advisory 3)

xio-udp.c

@@ -1,5 +1,5 @@
 /* source: xio-udp.c */
-/* Copyright Gerhard Rieger 2001-2009 */
+/* Copyright Gerhard Rieger 2001-2012 */
 /* Published under the GNU General Public License V.2, see file COPYING */
 
 /* this file contains the source for handling UDP addresses */
@@ -188,7 +188,8 @@ int xioopen_ipdgram_listen(int argc, const char *argv[], struct opt *opts,
    while (true) {	/* we loop with fork or prohibited packets */
       /* now wait for some packet on this datagram socket, get its sender
 	 address, connect there, and return */
-      int one = 1;
+      int reuseaddr = dofork;
+      int doreuseaddr = (dofork != 0);
       char infobuff[256];
       union sockaddr_union _sockname;
       union sockaddr_union *la = &_sockname;	/* local address */
@@ -197,12 +198,17 @@ int xioopen_ipdgram_listen(int argc, const char *argv[], struct opt *opts,
 	 return STAT_RETRYLATER;
       }
       /*0 Info4("socket(%d, %d, %d) -> %d", pf, socktype, ipproto, fd->stream.fd);*/
+      doreuseaddr |= (retropt_int(opts, OPT_SO_REUSEADDR, &reuseaddr) >= 0);
       applyopts(fd->stream.rfd, opts, PH_PASTSOCKET);
-      if (Setsockopt(fd->stream.rfd, opt_so_reuseaddr.major,
+      if (doreuseaddr) {
-		     opt_so_reuseaddr.minor, &one, sizeof(one)) < 0) {
+	 if (Setsockopt(fd->stream.rfd, opt_so_reuseaddr.major,
-	 Warn6("setsockopt(%d, %d, %d, {%d}, "F_Zd"): %s",
+			opt_so_reuseaddr.minor, &reuseaddr, sizeof(reuseaddr))
-	       fd->stream.rfd, opt_so_reuseaddr.major,
+	     < 0) {
-	       opt_so_reuseaddr.minor, one, sizeof(one), strerror(errno));
+	    Warn6("setsockopt(%d, %d, %d, {%d}, "F_Zd"): %s",
+		  fd->stream.rfd, opt_so_reuseaddr.major,
+		  opt_so_reuseaddr.minor, reuseaddr, sizeof(reuseaddr),
+		  strerror(errno));
+	 }
       }
       applyopts_cloexec(fd->stream.rfd, opts);
       applyopts(fd->stream.rfd, opts, PH_PREBIND);