Systemd will, by default, pass a socket that provides both IPv4 and
IPv6 services. RPC netconfig requires that sockets be either IPv4
or IPv6. Add a warning to rpcbind should the user encounter an issue.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>

--- a/src/rpcbind.c
+++ b/src/rpcbind.c	2014/12/10 13:48:28
@@ -50,6 +50,7 @@
 #include <sys/file.h>
 #include <sys/socket.h>
 #include <sys/un.h>
+#include <netinet/in.h>
 #include <rpc/rpc.h>
 #include <rpc/rpc_com.h>
 #ifdef PORTMAP
@@ -277,6 +285,31 @@
 }
 
 /*
+ * Normally systemd will open sockets in dual ipv4/ipv6 mode.
+ * That won't work with netconfig and we'll only match
+ * the ipv6 socket. Convert it to IPV6_V6ONLY and issue
+ * a warning for the user to fix their systemd config.
+ */
+static int
+handle_ipv6_socket(int fd)
+{
+        int opt;
+	socklen_t len = sizeof(opt);
+
+	if (getsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &opt, &len)) {
+                syslog(LOG_ERR, "failed to get ipv6 socket opts: %m");
+                return -1;
+	}
+
+	if (opt) /* socket is already in V6ONLY mode */
+                return 0;
+
+	syslog(LOG_ERR, "systemd has passed an IPv4/IPv6 dual-mode socket.");
+	syslog(LOG_ERR, "Please fix your systemd config by specifying IPv4 and IPv6 sockets separately and using BindIPv6Only=ipv6-only.");
+	return -1;
+}
+
+/*
  * Adds the entry into the rpcbind database.
  * If PORTMAP, then for UDP and TCP, it adds the entries for version 2 also
  * Returns 0 if succeeds, else fails
@@ -361,6 +394,9 @@
 			goto error;
 		}
 
+		if (sa.sa.sa_family == AF_INET6 && handle_ipv6_socket(fd))
+		        goto error;
+
 		/* Copy the address */
 		taddr.addr.maxlen = taddr.addr.len = addrlen;
 		taddr.addr.buf = malloc(addrlen);