net: mctp: avoid confusion over local/peer dest/source addresses

We have a double-swap of local and peer addresses in
mctp_alloc_local_tag; the arguments in both call sites are swapped, but
there is also a swap in the implementation of alloc_local_tag. This is
opaque because we're using source/dest address references, which don't
match the local/peer semantics.

Avoid this confusion by naming the arguments as 'local' and 'peer', and
remove the double swap. The calling order now matches mctp_key_alloc.
Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

include/net/mctp.h

@@ -87,7 +87,7 @@ struct mctp_sock {
 };
 
 /* Key for matching incoming packets to sockets or reassembly contexts.
- * Packets are matched on (src,dest,tag).
+ * Packets are matched on (peer EID, local EID, tag).
  *
  * Lifetime / locking requirements:
  *
@@ -254,7 +254,7 @@ int mctp_local_output(struct sock *sk, struct mctp_route *rt,
 
 void mctp_key_unref(struct mctp_sk_key *key);
 struct mctp_sk_key *mctp_alloc_local_tag(struct mctp_sock *msk,
-					 mctp_eid_t daddr, mctp_eid_t saddr,
+					 mctp_eid_t local, mctp_eid_t peer,
 					 bool manual, u8 *tagp);
 
 /* routing <--> device interface */

net/mctp/af_mctp.c

@@ -367,7 +367,7 @@ static int mctp_ioctl_alloctag(struct mctp_sock *msk, unsigned long arg)
 	if (ctl.flags)
 		return -EINVAL;
 
-	key = mctp_alloc_local_tag(msk, ctl.peer_addr, MCTP_ADDR_ANY,
+	key = mctp_alloc_local_tag(msk, MCTP_ADDR_ANY, ctl.peer_addr,
 				   true, &tag);
 	if (IS_ERR(key))
 		return PTR_ERR(key);

net/mctp/route.c

@@ -596,11 +596,11 @@ static void mctp_reserve_tag(struct net *net, struct mctp_sk_key *key,
 	refcount_inc(&key->refs);
 }
 
-/* Allocate a locally-owned tag value for (saddr, daddr), and reserve
+/* Allocate a locally-owned tag value for (local, peer), and reserve
  * it for the socket msk
  */
 struct mctp_sk_key *mctp_alloc_local_tag(struct mctp_sock *msk,
-					 mctp_eid_t daddr, mctp_eid_t saddr,
+					 mctp_eid_t local, mctp_eid_t peer,
 					 bool manual, u8 *tagp)
 {
 	struct net *net = sock_net(&msk->sk);
@@ -610,11 +610,11 @@ struct mctp_sk_key *mctp_alloc_local_tag(struct mctp_sock *msk,
 	u8 tagbits;
 
 	/* for NULL destination EIDs, we may get a response from any peer */
-	if (daddr == MCTP_ADDR_NULL)
-		daddr = MCTP_ADDR_ANY;
+	if (peer == MCTP_ADDR_NULL)
+		peer = MCTP_ADDR_ANY;
 
 	/* be optimistic, alloc now */
-	key = mctp_key_alloc(msk, saddr, daddr, 0, GFP_KERNEL);
+	key = mctp_key_alloc(msk, local, peer, 0, GFP_KERNEL);
 	if (!key)
 		return ERR_PTR(-ENOMEM);
 
@@ -635,8 +635,8 @@ struct mctp_sk_key *mctp_alloc_local_tag(struct mctp_sock *msk,
 		if (tmp->tag & MCTP_HDR_FLAG_TO)
 			continue;
 
-		if (!(mctp_address_matches(tmp->peer_addr, daddr) &&
-		      mctp_address_matches(tmp->local_addr, saddr)))
+		if (!(mctp_address_matches(tmp->peer_addr, peer) &&
+		      mctp_address_matches(tmp->local_addr, local)))
 			continue;
 
 		spin_lock(&tmp->lock);
@@ -924,7 +924,7 @@ int mctp_local_output(struct sock *sk, struct mctp_route *rt,
 			key = mctp_lookup_prealloc_tag(msk, daddr,
 						       req_tag, &tag);
 		else
-			key = mctp_alloc_local_tag(msk, daddr, saddr,
+			key = mctp_alloc_local_tag(msk, saddr, daddr,
 						   false, &tag);
 
 		if (IS_ERR(key)) {