MINOR: protocol: retrieve the family-specific fields from the family

We now take care of retrieving sock_family, l3_addrlen, bind(),
addrcmp(), get_src() and get_dst() from the protocol family and
not just the protocol itself. There are very few places, this was
only seldom used. Interestingly in sock_inet.c used to rely on
->sock_family instead of ->sock_domain, and sock_unix.c used to
hard-code PF_UNIX instead of using ->sock_domain.

Also it appears obvious we have something wrong it the protocol
selection algorithm because sock_domain is the one set to the custom
protocols while it ought to be sock_family instead, which would avoid
having to hard-code some conversions for UDP namely.
diff --git a/src/protocol.c b/src/protocol.c
index a4e93e2..7485870 100644
--- a/src/protocol.c
+++ b/src/protocol.c
@@ -82,7 +82,7 @@
 				handler = syslog_fd_handler;
 			}
 
-			lerr = proto->bind(receiver, handler, &errmsg);
+			lerr = proto->fam->bind(receiver, handler, &errmsg);
 			err |= lerr;
 
 			/* errors are reported if <verbose> is set or if they are fatal */
diff --git a/src/sock.c b/src/sock.c
index 9431e75..3e414a8 100644
--- a/src/sock.c
+++ b/src/sock.c
@@ -363,7 +363,7 @@
 	int ns_namelen = 0;
 	int ret = -1;
 
-	if (!rx->proto->addrcmp)
+	if (!rx->proto->fam->addrcmp)
 		return -1;
 
 	if (rx->proto->sock_type == SOCK_DGRAM)
@@ -397,7 +397,7 @@
 #ifdef USE_NS
 		    (!ns_namelen || strcmp(rx->settings->netns->node.key, xfer_sock->namespace) == 0) &&
 #endif
-		    rx->proto->addrcmp(&xfer_sock->addr, &rx->addr) == 0)
+		    rx->proto->fam->addrcmp(&xfer_sock->addr, &rx->addr) == 0)
 			break;
 		xfer_sock = xfer_sock->next;
 	}
diff --git a/src/sock_inet.c b/src/sock_inet.c
index 09ff71e..7c814d0 100644
--- a/src/sock_inet.c
+++ b/src/sock_inet.c
@@ -263,7 +263,7 @@
 	struct sockaddr_storage addr_inet = rx->addr;
 
 	/* force to classic sock family, not AF_CUST_* */
-	addr_inet.ss_family = rx->proto->sock_family;
+	addr_inet.ss_family = rx->proto->fam->sock_family;
 
 	/* ensure we never return garbage */
 	if (errmsg)
@@ -289,7 +289,7 @@
 	ext = (fd >= 0);
 
 	if (!ext) {
-		fd = my_socketat(rx->settings->netns, rx->proto->sock_family,
+		fd = my_socketat(rx->settings->netns, rx->proto->fam->sock_domain,
 		                 rx->proto->sock_type, rx->proto->sock_prot);
 		if (fd == -1) {
 			err |= ERR_RETRYABLE | ERR_ALERT;
@@ -367,7 +367,7 @@
 	}
 #endif
 
-	if (!ext && bind(fd, (struct sockaddr *)&addr_inet, rx->proto->sock_addrlen) == -1) {
+	if (!ext && bind(fd, (struct sockaddr *)&addr_inet, rx->proto->fam->sock_addrlen) == -1) {
 		err |= ERR_RETRYABLE | ERR_ALERT;
 		memprintf(errmsg, "cannot bind socket");
 		goto bind_close_return;
diff --git a/src/sock_unix.c b/src/sock_unix.c
index 4620b74..8bdfed9 100644
--- a/src/sock_unix.c
+++ b/src/sock_unix.c
@@ -218,7 +218,7 @@
 	addr.sun_family = AF_UNIX;
 
 	/* WT: shouldn't we use my_socketat(rx->netns) here instead ? */
-	fd = socket(PF_UNIX, SOCK_STREAM, 0);
+	fd = socket(rx->proto->fam->sock_domain, rx->proto->sock_type, rx->proto->sock_prot);
 	if (fd < 0) {
 		err |= ERR_FATAL | ERR_ALERT;
 		memprintf(errmsg, "cannot create receiving socket");