iscsi-target: ST response on IN6ADDR_ANY socket

Odd little issue, found that if you create an IPv6 portal bound to the
IN6ADDR_ANY wildcard address it will accept IPv4 connections (as long as
bindv6only isn't set globally) but respond to SendTargets requests with
an IPv4-mapped IPv6 address.

Example over loopback:

In targetcli create a wildcard IPv6 portal
/iscsi/iqn.../portals/> create ::
Which should create a portal [::]:3260

Initiate SendTargets discovery to the portal using an IPv4 address
# iscsiadm -m discovery -t st -p 127.0.0.1
The response formats TargetAddress as [::ffff:127.0.0.1]:3260,1

This still works and uses v4 on the network between two v6 sockets, but
only if the initiator supports IPv6 with v4-mapped addresses.

This change detects v4-mapped address on v6 sockets for the wildcard
case, and instead formats the TargetAddress response as an IPv4 address.

In order to not further complicate iscsit_build_sendtargets_response,
I've actually simplified it by moving the bracket wrapping of IPv6
address into iscsit_accept_np where local_ip and login_ip strings are
set. That also simplifies iscsi_stat_tgt_attr_show_attr_fail_intr_addr.

Side effect of the string format change is that
lio_target_nacl_show_info will now print login_ip bracket wrapped for
IPv6 connections, as will a few debug prints.

Signed-off-by: Chris Leech <[e-mail]>
Signed-off-by: Nicholas Bellinger <[e-mail]>

drivers/target/iscsi/iscsi_target.c

···
 				bool inaddr_any = iscsit_check_inaddr_any(np);
 
 				len = sprintf(buf, "TargetAddress="
-					"%s%s%s:%hu,%hu",
-					(np->np_sockaddr.ss_family == AF_INET6) ?
-					"[" : "", (inaddr_any == false) ?
+					"%s:%hu,%hu",
+					(inaddr_any == false) ?
 						np->np_ip : conn->local_ip,
-					(np->np_sockaddr.ss_family == AF_INET6) ?
-					"]" : "", (inaddr_any == false) ?
+					(inaddr_any == false) ?
 						np->np_port : conn->local_port,
 					tpg->tpgt);
 				len += 1;

drivers/target/iscsi/iscsi_target_login.c

···
 		rc = conn->sock->ops->getname(conn->sock,
 				(struct sockaddr *)&sock_in6, &err, 1);
 		if (!rc) {
-			snprintf(conn->login_ip, sizeof(conn->login_ip), "%pI6c",
-				&sock_in6.sin6_addr.in6_u);
+			if (!ipv6_addr_v4mapped(&sock_in6.sin6_addr))
+				snprintf(conn->login_ip, sizeof(conn->login_ip), "[%pI6c]",
+					&sock_in6.sin6_addr.in6_u);
+			else
+				snprintf(conn->login_ip, sizeof(conn->login_ip), "%pI4",
+					&sock_in6.sin6_addr.s6_addr32[3]);
 			conn->login_port = ntohs(sock_in6.sin6_port);
 		}
 
 		rc = conn->sock->ops->getname(conn->sock,
 				(struct sockaddr *)&sock_in6, &err, 0);
 		if (!rc) {
-			snprintf(conn->local_ip, sizeof(conn->local_ip), "%pI6c",
-				&sock_in6.sin6_addr.in6_u);
+			if (!ipv6_addr_v4mapped(&sock_in6.sin6_addr))
+				snprintf(conn->local_ip, sizeof(conn->local_ip), "[%pI6c]",
+					&sock_in6.sin6_addr.in6_u);
+			else
+				snprintf(conn->local_ip, sizeof(conn->local_ip), "%pI4",
+					&sock_in6.sin6_addr.s6_addr32[3]);
 			conn->local_port = ntohs(sock_in6.sin6_port);
 		}
 	} else {

drivers/target/iscsi/iscsi_target_stat.c

···
 	int ret;
 
 	spin_lock(&lstat->lock);
-	if (lstat->last_intr_fail_ip_family == AF_INET6) {
-		ret = snprintf(page, PAGE_SIZE, "[%s]\n",
-			       lstat->last_intr_fail_ip_addr);
-	} else {
-		ret = snprintf(page, PAGE_SIZE, "%s\n",
-			       lstat->last_intr_fail_ip_addr);
-	}
+	ret = snprintf(page, PAGE_SIZE, "%s\n", lstat->last_intr_fail_ip_addr);
 	spin_unlock(&lstat->lock);
 
 	return ret;