rx: Don't send packets to localhost if -rxbind set

For some platforms (SOLARIS, FBSD), shutting down the libafs client
currently involves sending a packet to localhost to wakeup the listener
thread. If rx is bound to a specific host address (the -rxbind option
was passed to afsd), this won't work, because rx won't receive packets
sent to localhost. This results in the client hanging forever when
trying to 'umount afs', until a packet is otherwise sent to the rx
socket.

To fix this, send the packet to the bound host address instead, if
-rxbind was given. Otherwise, send the packet to localhost, like before.

Introduce the small helper function rxi_GetLocalAddr() to consolidate
the logic of what address to use.

Change-Id: I26fa5194b726ed753779faa07142fec647228b44
Reviewed-on: https://gerrit.openafs.org/15906
Reviewed-by: Marcio Brito Barbosa <mbarbosa@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
Tested-by: Andrew Deason <adeason@sinenomine.net>

src/rx/FBSD/rx_knet.c

@@ -108,8 +108,7 @@ osi_StopListener(void)
     bzero(&taddr, sizeof(taddr));
     taddr.sin_len = sizeof(struct sockaddr_in);
     taddr.sin_family = AF_INET;
-    taddr.sin_port = rx_port;
-    taddr.sin_addr.s_addr = htonl(0x7f000001);	/* no place like localhost */
+    rxi_GetLocalAddr(&taddr);
     bzero(&dvec, sizeof(dvec));
     dvec.iov_base = &c;
     dvec.iov_len = 1;

src/rx/SOLARIS/rx_knet.c

@@ -451,8 +451,7 @@ osi_FreeSocket(osi_socket asocket)
     AFS_STATCNT(osi_FreeSocket);
 
     taddr.sin_family = AF_INET;
-    taddr.sin_port = rx_port;
-    taddr.sin_addr.s_addr = htonl(0x7f000001);
+    rxi_GetLocalAddr(&taddr);
 
     dvec.iov_base = &c;
     dvec.iov_len = 1;

src/rx/rx.c

@@ -9679,3 +9679,25 @@ rxi_NetSend(osi_socket socket, void *addr, struct iovec *dvec,
     return ESHUTDOWN;
 #endif
 }
+
+/*
+ * Get our local address (the address to use to send packets to ourselves). If
+ * rx_InitHost() was given a host to bind to, we use that host address;
+ * otherwise use 127.0.0.1. The port is the port we are actually bound to.
+ *
+ * @param[out] sin  host/port populated with the address to use
+ *
+ * @pre rx_InitHost() called successfully
+ */
+void
+rxi_GetLocalAddr(struct sockaddr_in *sin)
+{
+    if (rx_host != 0) {
+	/* If we're bound to an address, use that address as localhost. */
+	sin->sin_addr.s_addr = rx_host;
+    } else {
+	/* Otherwise, use 127.0.0.1. */
+	sin->sin_addr.s_addr = htonl(0x7f000001);
+    }
+    sin->sin_port = rx_port;
+}