Merge branch 'net-mctp-add-support-for-gateway-routing'

Jeremy Kerr says:

====================
net: mctp: Add support for gateway routing

This series adds a gateway route type for the MCTP core, allowing
non-local EIDs as the match for a route.

Example setup using the mctp tools:

    mctp route add 9 via mctpi2c0
    mctp neigh add 9 dev mctpi2c0 lladdr 0x1d
    mctp route add 10 gw 9

- will route packets to eid 10 through mctpi2c0, using a dest lladdr
of 0x1d (ie, that of the directly-attached eid 9).

The core change to support this is the introduction of a struct
mctp_dst, which represents the result of a route lookup. Since this
involves a bit of surgery through the routing code, we add a few tests
along the way.

We're introducing an ABI change in the new RTM_{NEW,GET,DEL}ROUTE
netlink formats, with the support for a RTA_GATEWAY attribute. Because
we need a network ID specified to fully-qualify a gateway EID, the
RTA_GATEWAY attribute carries the (net, eid) tuple in full:

    struct mctp_fq_addr {
        unsigned int net;
        mctp_eid_t eid;
    }

Of course, any questions, comments etc are most welcome.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
====================

Link: https://patch.msgid.link/20250702-dev-forwarding-v5-0-1468191da8a4@codeconstruct.com.au
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 26 insertions, 40 deletions

diff --git a/net/mctp/af_mctp.c b/net/mctp/af_mctp.c
index 9b12ca97f412..aef74308c18e 100644
--- a/net/mctp/af_mctp.c
+++ b/net/mctp/af_mctp.c
@@ -97,8 +97,8 @@ static int mctp_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 	struct sock *sk = sock->sk;
 	struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
 	struct mctp_skb_cb *cb;
-	struct mctp_route *rt;
 	struct sk_buff *skb = NULL;
+	struct mctp_dst dst;
 	int hlen;
 
 	if (addr) {
@@ -133,34 +133,30 @@ static int mctp_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 	if (msk->addr_ext && addrlen >= sizeof(struct sockaddr_mctp_ext)) {
 		DECLARE_SOCKADDR(struct sockaddr_mctp_ext *,
 				 extaddr, msg->msg_name);
-		struct net_device *dev;
-
-		rc = -EINVAL;
-		rcu_read_lock();
-		dev = dev_get_by_index_rcu(sock_net(sk), extaddr->smctp_ifindex);
-		/* check for correct halen */
-		if (dev && extaddr->smctp_halen == dev->addr_len) {
-			hlen = LL_RESERVED_SPACE(dev) + sizeof(struct mctp_hdr);
-			rc = 0;
-		}
-		rcu_read_unlock();
+
+		if (!mctp_sockaddr_ext_is_ok(extaddr))
+			return -EINVAL;
+
+		rc = mctp_dst_from_extaddr(&dst, sock_net(sk),
+					   extaddr->smctp_ifindex,
+					   extaddr->smctp_halen,
+					   extaddr->smctp_haddr);
 		if (rc)
-			goto err_free;
-		rt = NULL;
+			return rc;
+
 	} else {
-		rt = mctp_route_lookup(sock_net(sk), addr->smctp_network,
-				       addr->smctp_addr.s_addr);
-		if (!rt) {
-			rc = -EHOSTUNREACH;
-			goto err_free;
-		}
-		hlen = LL_RESERVED_SPACE(rt->dev->dev) + sizeof(struct mctp_hdr);
+		rc = mctp_route_lookup(sock_net(sk), addr->smctp_network,
+				       addr->smctp_addr.s_addr, &dst);
+		if (rc)
+			return rc;
 	}
 
+	hlen = LL_RESERVED_SPACE(dst.dev->dev) + sizeof(struct mctp_hdr);
+
 	skb = sock_alloc_send_skb(sk, hlen + 1 + len,
 				  msg->msg_flags & MSG_DONTWAIT, &rc);
 	if (!skb)
-		return rc;
+		goto err_release_dst;
 
 	skb_reserve(skb, hlen);
 
@@ -175,30 +171,16 @@ static int mctp_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 	cb = __mctp_cb(skb);
 	cb->net = addr->smctp_network;
 
-	if (!rt) {
-		/* fill extended address in cb */
-		DECLARE_SOCKADDR(struct sockaddr_mctp_ext *,
-				 extaddr, msg->msg_name);
-
-		if (!mctp_sockaddr_ext_is_ok(extaddr) ||
-		    extaddr->smctp_halen > sizeof(cb->haddr)) {
-			rc = -EINVAL;
-			goto err_free;
-		}
-
-		cb->ifindex = extaddr->smctp_ifindex;
-		/* smctp_halen is checked above */
-		cb->halen = extaddr->smctp_halen;
-		memcpy(cb->haddr, extaddr->smctp_haddr, cb->halen);
-	}
-
-	rc = mctp_local_output(sk, rt, skb, addr->smctp_addr.s_addr,
+	rc = mctp_local_output(sk, &dst, skb, addr->smctp_addr.s_addr,
 			       addr->smctp_tag);
 
+	mctp_dst_release(&dst);
 	return rc ? : len;
 
 err_free:
 	kfree_skb(skb);
+err_release_dst:
+	mctp_dst_release(&dst);
 	return rc;
 }
 
@@ -793,3 +775,7 @@ MODULE_DESCRIPTION("MCTP core");
 MODULE_AUTHOR("Jeremy Kerr <jk@codeconstruct.com.au>");
 
 MODULE_ALIAS_NETPROTO(PF_MCTP);
+
+#if IS_ENABLED(CONFIG_MCTP_TEST)
+#include "test/sock-test.c"
+#endif