SCTP service name resolution falls back to socktype and protocol 0

CHANGES

@@ -32,6 +32,12 @@ Porting:
 	Added configure option --enable-openssl-base to specify the location of
 	a non-OS OpenSSL installation
 
+	There are systems whose kernel understands SCTP but getaddrinfo does
+	not. As workaround after EIA_SOCKTYPE on name and service resolution
+	fall back to ai_socktype=0; if it fails with EAI_SERVICE, set
+	ai_protocol=0 and try again
+	Test: SCTP_SERVICENAME
+
 Testing:
 	test.sh now produces a list of tests that could not be performed for
 	any reason. This helps to analyse these cases.

test.sh

@@ -13573,6 +13573,48 @@ esac
 N=$((N+1))
 
 
+# Currently (2020) SCTP has not found its way into main distributions
+# /etc/services file. A fallback mechanism has been implemented in Socat
+# that allows use of TCP service names when service resolution for SCTP failed.
+# Furthermore, older getaddrinfo() implementations to not handle SCTP as SOCK_STREAM
+# at all, fall back to unspecified socktype then.
+NAME=SCTP_SERVICENAME
+case "$TESTS" in
+*%$N%*|*%functions%*|*%socket%*|*%sctp%*|*%$NAME%*)
+TEST="$NAME: Service name resolution works with SCTP"
+# invoke socat with address SCTP4-CONNECT:$LOCALHOST:http; when this does fails with
+# "Connection refused", or does not fail at all, the test succeeded
+if ! eval $NUMCOND; then :;
+elif ! runssctp4 "$((PORT))" >/dev/null; then
+    $PRINTF "test $F_n $TEST... ${YELLOW}SCTP4 not available${NORMAL}\n" $N
+    numCANT=$((numCANT+1))
+    listCANT="$listCANT $N"
+else
+tf="$td/test$N.stdout"
+te="$td/test$N.stderr"
+tdiff="$td/test$N.diff"
+CMD0="$TRACE $SOCAT $opts -u /dev/null SCTP4-CONNECT:$LOCALHOST:http"
+printf "test $F_n $TEST... " $N
+$CMD0 >/dev/null 2>"${te}0"
+if [ $? -eq 0 ]; then
+    $PRINTF "$OK\n"
+    numOK=$((numOK+1))
+elif grep -q "Connection refused" ${te}0; then
+    $PRINTF "$OK\n"
+    numOK=$((numOK+1))
+else
+    $PRINTF "$FAILED\n"
+    echo "$CMD0"
+    cat "${te}0"
+    numFAIL=$((numFAIL+1))
+    listFAIL="$listFAIL $N"
+fi
+fi # NUMCOND
+ ;;
+esac
+N=$((N+1))
+
+
 ##################################################################################
 #=================================================================================
 # here come tests that might affect your systems integrity. Put normal tests

xio-ip.c

@@ -202,9 +202,6 @@ int xiogetaddrinfo(const char *node, const char *service,
    if (node != NULL || service != NULL) {
       struct addrinfo *record;
 
-      /* here was code that helped SCTP to use service names.
-	 If you need this feature enhance your /etc/services with sctp entries */
-
       hints.ai_flags |= AI_PASSIVE;
       hints.ai_family = family;
       hints.ai_socktype = socktype;
@@ -214,7 +211,19 @@ int xiogetaddrinfo(const char *node, const char *service,
       hints.ai_canonname = NULL;
       hints.ai_next = NULL;
 
-      if ((error_num = Getaddrinfo(node, service, &hints, &res)) != 0) {
+      do {
+	error_num = Getaddrinfo(node, service, &hints, &res);
+	if (error_num == 0)  break;
+	if (error_num == EAI_SOCKTYPE && socktype != 0) {
+	   /* there are systems where kernel goes SCTP but not getaddrinfo() */
+	   hints.ai_socktype = 0;
+	   continue;
+	}
+	if (error_num == EAI_SERVICE && protocol != 0) {
+	   hints.ai_protocol = 0;
+	   continue;
+	}
+	if (error_num != 0) {
 	 Error7("getaddrinfo(\"%s\", \"%s\", {%d,%d,%d,%d}, {}): %s",
 		node?node:"NULL", service?service:"NULL",
 		hints.ai_flags, hints.ai_family,
@@ -232,6 +241,7 @@ int xiogetaddrinfo(const char *node, const char *service,
 #endif
 	 return STAT_RETRYLATER;
 	}
+      } while (1);
       service = NULL;	/* do not resolve later again */
 
       record = res;