Small fix in sockets if only loopback interface is up.

2 files changed, 21 insertions, 1 deletions

diff --git a/ChangeLog b/ChangeLog
index a5fd076d..b467eb23 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2018-02-09         Arnold D. Robbins     <arnold@skeeve.com>
+
+	* io.c (socketopen): Rearrange assigning the flags to use
+	AI_ADDRCONFIG only if family is AF_UNSPEC. Thanks to
+	Houder <houder@xs4all.nl> for the report and initial
+	code suggestion.
+
 2018-02-07         Andrew J. Schorr      <aschorr@telemetry-investments.com>
 
 	Print +"01" should print "1", not "01".
diff --git a/io.c b/io.c
index befc20a1..f09c4a02 100644
--- a/io.c
+++ b/io.c
@@ -1579,10 +1579,23 @@ socketopen(int family, int type, const char *localpname,
 	int any_remote_host = (strcmp(remotehostname, "0") == 0);
 
 	memset(& lhints, '\0', sizeof (lhints));
-	lhints.ai_flags = AI_PASSIVE | AI_ADDRCONFIG;
+
 	lhints.ai_socktype = type;
 	lhints.ai_family = family;
 
+	/*
+         * If only the loopback interface is up and hints.ai_flags has
+	 * AI_ADDRCONFIG, getaddrinfo() will succeed and return all wildcard
+	 * addresses, but only if hints.ai_family == AF_UNSPEC
+	 *
+	 * Do return the wildcard address in case the loopback interface
+	 * is the only one that is up (and
+	 * hints.ai_family == either AF_INET4 or AF_INET6)
+         */
+	lhints.ai_flags = AI_PASSIVE;
+	if (lhints.ai_family == AF_UNSPEC)
+		lhints.ai_flags |= AI_ADDRCONFIG;
+
 	lerror = getaddrinfo(NULL, localpname, & lhints, & lres);
 	if (lerror) {
 		if (strcmp(localpname, "0") != 0) {