[PATCH net-next v3 0/8] net: mctp: Improved bind handling

[PATCH net-next v3 0/8] net: mctp: Improved bind handling

[Matt Johnston]

This series improves a couple of aspects of MCTP bind() handling.

MCTP wasn't checking whether the same MCTP type was bound by multiple
sockets. That would result in messages being received by an arbitrary
socket, which isn't useful behaviour. Instead it makes more sense to
have the duplicate binds fail, the same as other network protocols.
An exception is made for more-specific binds to particular MCTP
addresses.

It is also useful to be able to limit a bind to only receive incoming
request messages (MCTP TO bit set) from a specific peer+type, so that
individual processes can communicate with separate MCTP peers. One
example is a PLDM firmware update requester, which will initiate
communication with a device, and then the device will connect back to the
requester process. 

These limited binds are implemented by a connect() call on the socket
prior to bind. connect() isn't used in the general case for MCTP, since
a plain send() wouldn't provide the required MCTP tag argument for
addressing.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
---
Changes in v3:
- Rebased to net-next
- kunit tests have been updated for MCTP gateway routing changes
- Bind conflict tests are now in the new mctp/tests/sock-test.c
- Added patch for mctp_test_route_extaddr_input kunit socket cleanup
  (fixes MCTP gateway routing change in net-next, required by tests in
  this series)
- Link to v2: https://lore.kernel.org/r/20250707-mctp-bind-v2-0-fbaed8c1fb4d@codeconstruct.com.au

Changes in v2:
- Use DECLARE_HASHTABLE
- Remove unused kunit test case
- Avoid kunit test snprintf truncation warning
- Fix lines >80 characters
- Link to v1: https://lore.kernel.org/r/20250703-mctp-bind-v1-0-bb7e97c24613@codeconstruct.com.au

---
Matt Johnston (8):
      net: mctp: mctp_test_route_extaddr_input cleanup
      net: mctp: Prevent duplicate binds
      net: mctp: Treat MCTP_NET_ANY specially in bind()
      net: mctp: Add test for conflicting bind()s
      net: mctp: Use hashtable for binds
      net: mctp: Allow limiting binds to a peer address
      net: mctp: Test conflicts of connect() with bind()
      net: mctp: Add bind lookup test

 include/net/mctp.h         |   5 +-
 include/net/netns/mctp.h   |  20 ++++-
 net/mctp/af_mctp.c         | 146 +++++++++++++++++++++++++++++++---
 net/mctp/route.c           |  85 ++++++++++++++++----
 net/mctp/test/route-test.c | 194 ++++++++++++++++++++++++++++++++++++++++++++-
 net/mctp/test/sock-test.c  | 167 ++++++++++++++++++++++++++++++++++++++
 net/mctp/test/utils.c      |  36 +++++++++
 net/mctp/test/utils.h      |  17 ++++
 8 files changed, 635 insertions(+), 35 deletions(-)
---
base-commit: ea988b450690448d5b12ce743a598ade7a8c34b1
change-id: 20250321-mctp-bind-e77968f180fd

Best regards,
-- 
Matt Johnston <matt@codeconstruct.com.au>

[PATCH net-next v3 1/8] net: mctp: mctp_test_route_extaddr_input cleanup

[Matt Johnston]

The sock was not being released. Other than leaking, the stale socket
will conflict with subsequent bind() calls in unrelated MCTP tests.

Fixes: 11b67f6f22d6 ("net: mctp: test: Add extaddr routing output test")
Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>

---
Added in v3. The problem was introduced in current net-next so
this patch isn't needed in the stable tree.
---
 net/mctp/test/route-test.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/mctp/test/route-test.c b/net/mctp/test/route-test.c
index 7a398f41b6216afef72adecf118199753ed1bfea..12811032a2696167b4f319cbc9c81fef4cb2d951 100644
--- a/net/mctp/test/route-test.c
+++ b/net/mctp/test/route-test.c
@@ -1164,8 +1164,6 @@ static void mctp_test_route_extaddr_input(struct kunit *test)
 	rc = mctp_dst_input(&dst, skb);
 	KUNIT_ASSERT_EQ(test, rc, 0);
 
-	mctp_test_dst_release(&dst, &tpq);
-
 	skb2 = skb_recv_datagram(sock->sk, MSG_DONTWAIT, &rc);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, skb2);
 	KUNIT_ASSERT_EQ(test, skb2->len, len);
@@ -1179,8 +1177,8 @@ static void mctp_test_route_extaddr_input(struct kunit *test)
 	KUNIT_EXPECT_EQ(test, cb2->halen, sizeof(haddr));
 	KUNIT_EXPECT_MEMEQ(test, cb2->haddr, haddr, sizeof(haddr));
 
-	skb_free_datagram(sock->sk, skb2);
-	mctp_test_destroy_dev(dev);
+	kfree_skb(skb2);
+	__mctp_route_test_fini(test, dev, &dst, &tpq, sock);
 }
 
 static void mctp_test_route_gw_lookup(struct kunit *test)

-- 
2.43.0

Re: [PATCH net-next v3 1/8] net: mctp: mctp_test_route_extaddr_input cleanup

[Simon Horman]

On Wed, Jul 09, 2025 at 04:31:02PM +0800, Matt Johnston wrote:
> The sock was not being released. Other than leaking, the stale socket
> will conflict with subsequent bind() calls in unrelated MCTP tests.
> 
> Fixes: 11b67f6f22d6 ("net: mctp: test: Add extaddr routing output test")

Hi Matt,

What I assume is that commit seems to have a different hash in net-next.

Fixes: 46ee16462fed ("net: mctp: test: Add extaddr routing output test")

> Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
> 
> ---
> Added in v3. The problem was introduced in current net-next so
> this patch isn't needed in the stable tree.

Ack, thanks for noting that.

...

Re: [PATCH net-next v3 1/8] net: mctp: mctp_test_route_extaddr_input cleanup

[Matt Johnston]

Hi Simon,

On Wed, 2025-07-09 at 10:03 +0100, Simon Horman wrote:
> > 
> > Fixes: 11b67f6f22d6 ("net: mctp: test: Add extaddr routing output test")
> 
> Hi Matt,
> 
> What I assume is that commit seems to have a different hash in net-next.
> 
> Fixes: 46ee16462fed ("net: mctp: test: Add extaddr routing output test")

Yes that's correct, sorry I missed updating that.
I'll fix it in v4.

Thanks,
Matt

Re: [PATCH net-next v3 1/8] net: mctp: mctp_test_route_extaddr_input cleanup

[Simon Horman]

On Wed, Jul 09, 2025 at 05:06:44PM +0800, Matt Johnston wrote:
> Hi Simon,
> 
> On Wed, 2025-07-09 at 10:03 +0100, Simon Horman wrote:
> > > 
> > > Fixes: 11b67f6f22d6 ("net: mctp: test: Add extaddr routing output test")
> > 
> > Hi Matt,
> > 
> > What I assume is that commit seems to have a different hash in net-next.
> > 
> > Fixes: 46ee16462fed ("net: mctp: test: Add extaddr routing output test")
> 
> Yes that's correct, sorry I missed updating that.
> I'll fix it in v4.

Thanks. Stuff happens.

[PATCH net-next v3 2/8] net: mctp: Prevent duplicate binds

[Matt Johnston]

Disallow bind() calls that have the same arguments as existing bound
sockets.  Previously multiple sockets could bind() to the same
type/local address, with an arbitrary socket receiving matched messages.

This is only a partial fix, a future commit will define precedence order
for MCTP_ADDR_ANY versus specific EID bind(), which are allowed to exist
together.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
---
 net/mctp/af_mctp.c | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/net/mctp/af_mctp.c b/net/mctp/af_mctp.c
index aef74308c18e3273008cb84aabe23ff700d0f842..0d073bc32ec17905ac0118d1aa653a46d829b150 100644
--- a/net/mctp/af_mctp.c
+++ b/net/mctp/af_mctp.c
@@ -73,7 +73,6 @@ static int mctp_bind(struct socket *sock, struct sockaddr *addr, int addrlen)
 
 	lock_sock(sk);
 
-	/* TODO: allow rebind */
 	if (sk_hashed(sk)) {
 		rc = -EADDRINUSE;
 		goto out_release;
@@ -611,15 +610,36 @@ static void mctp_sk_close(struct sock *sk, long timeout)
 static int mctp_sk_hash(struct sock *sk)
 {
 	struct net *net = sock_net(sk);
+	struct sock *existing;
+	struct mctp_sock *msk;
+	int rc;
+
+	msk = container_of(sk, struct mctp_sock, sk);
 
 	/* Bind lookup runs under RCU, remain live during that. */
 	sock_set_flag(sk, SOCK_RCU_FREE);
 
 	mutex_lock(&net->mctp.bind_lock);
-	sk_add_node_rcu(sk, &net->mctp.binds);
-	mutex_unlock(&net->mctp.bind_lock);
 
-	return 0;
+	/* Prevent duplicate binds. */
+	sk_for_each(existing, &net->mctp.binds) {
+		struct mctp_sock *mex =
+			container_of(existing, struct mctp_sock, sk);
+
+		if (mex->bind_type == msk->bind_type &&
+		    mex->bind_addr == msk->bind_addr &&
+		    mex->bind_net == msk->bind_net) {
+			rc = -EADDRINUSE;
+			goto out;
+		}
+	}
+
+	sk_add_node_rcu(sk, &net->mctp.binds);
+	rc = 0;
+
+out:
+	mutex_unlock(&net->mctp.bind_lock);
+	return rc;
 }
 
 static void mctp_sk_unhash(struct sock *sk)

-- 
2.43.0

[PATCH net-next v3 3/8] net: mctp: Treat MCTP_NET_ANY specially in bind()

[Matt Johnston]

When a specific EID is passed as a bind address, it only makes sense to
interpret with an actual network ID, so resolve that to the default
network at bind time.

For bind address of MCTP_ADDR_ANY, we want to be able to capture traffic
to any network and address, so keep the current behaviour of matching
traffic from any network interface (don't interpret MCTP_NET_ANY as
the default network ID).

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
---
 net/mctp/af_mctp.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/net/mctp/af_mctp.c b/net/mctp/af_mctp.c
index 0d073bc32ec17905ac0118d1aa653a46d829b150..20edaf840a607700c04b740708763fbd02a2df47 100644
--- a/net/mctp/af_mctp.c
+++ b/net/mctp/af_mctp.c
@@ -53,6 +53,7 @@ static int mctp_bind(struct socket *sock, struct sockaddr *addr, int addrlen)
 {
 	struct sock *sk = sock->sk;
 	struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
+	struct net *net = sock_net(&msk->sk);
 	struct sockaddr_mctp *smctp;
 	int rc;
 
@@ -77,8 +78,21 @@ static int mctp_bind(struct socket *sock, struct sockaddr *addr, int addrlen)
 		rc = -EADDRINUSE;
 		goto out_release;
 	}
-	msk->bind_net = smctp->smctp_network;
+
 	msk->bind_addr = smctp->smctp_addr.s_addr;
+
+	/* MCTP_NET_ANY with a specific EID is resolved to the default net
+	 * at bind() time.
+	 * For bind_addr=MCTP_ADDR_ANY it is handled specially at route
+	 * lookup time.
+	 */
+	if (smctp->smctp_network == MCTP_NET_ANY &&
+	    msk->bind_addr != MCTP_ADDR_ANY) {
+		msk->bind_net = mctp_default_net(net);
+	} else {
+		msk->bind_net = smctp->smctp_network;
+	}
+
 	msk->bind_type = smctp->smctp_type & 0x7f; /* ignore the IC bit */
 
 	rc = sk->sk_prot->hash(sk);

-- 
2.43.0

[PATCH net-next v3 4/8] net: mctp: Add test for conflicting bind()s

[Matt Johnston]

Test pairwise combinations of bind addresses and types.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>

---
v3:
- Moved test code to mctp/test/sock-test.c recently added in
  net-next, common bind test code in mctp/test/utils.c
v2:
- Remove unused bind test case
- Fix line lengths
---
 net/mctp/test/sock-test.c | 130 ++++++++++++++++++++++++++++++++++++++++++++++
 net/mctp/test/utils.c     |  22 ++++++++
 net/mctp/test/utils.h     |  10 ++++
 3 files changed, 162 insertions(+)

diff --git a/net/mctp/test/sock-test.c b/net/mctp/test/sock-test.c
index 4eb3a724dca39eb22615cbfc1201b45ee4c78d16..0cfc337be687e7ad903023d2fae9f12f75628532 100644
--- a/net/mctp/test/sock-test.c
+++ b/net/mctp/test/sock-test.c
@@ -215,9 +215,139 @@ static void mctp_test_sock_recvmsg_extaddr(struct kunit *test)
 	__mctp_sock_test_fini(test, dev, rt, sock);
 }
 
+static const struct mctp_test_bind_setup bind_addrany_netdefault_type1 = {
+	.bind_addr = MCTP_ADDR_ANY, .bind_net = MCTP_NET_ANY, .bind_type = 1,
+};
+
+static const struct mctp_test_bind_setup bind_addrany_net2_type1 = {
+	.bind_addr = MCTP_ADDR_ANY, .bind_net = 2, .bind_type = 1,
+};
+
+/* 1 is default net */
+static const struct mctp_test_bind_setup bind_addr8_net1_type1 = {
+	.bind_addr = 8, .bind_net = 1, .bind_type = 1,
+};
+
+static const struct mctp_test_bind_setup bind_addrany_net1_type1 = {
+	.bind_addr = MCTP_ADDR_ANY, .bind_net = 1, .bind_type = 1,
+};
+
+/* 2 is an arbitrary net */
+static const struct mctp_test_bind_setup bind_addr8_net2_type1 = {
+	.bind_addr = 8, .bind_net = 2, .bind_type = 1,
+};
+
+static const struct mctp_test_bind_setup bind_addr8_netdefault_type1 = {
+	.bind_addr = 8, .bind_net = MCTP_NET_ANY, .bind_type = 1,
+};
+
+static const struct mctp_test_bind_setup bind_addrany_net2_type2 = {
+	.bind_addr = MCTP_ADDR_ANY, .bind_net = 2, .bind_type = 2,
+};
+
+struct mctp_bind_pair_test {
+	const struct mctp_test_bind_setup *bind1;
+	const struct mctp_test_bind_setup *bind2;
+	int error;
+};
+
+/* Pairs of binds and whether they will conflict */
+static const struct mctp_bind_pair_test mctp_bind_pair_tests[] = {
+	/* Both ADDR_ANY, conflict */
+	{ &bind_addrany_netdefault_type1, &bind_addrany_netdefault_type1,
+	  EADDRINUSE },
+	/* Same specific EID, conflict */
+	{ &bind_addr8_netdefault_type1, &bind_addr8_netdefault_type1,
+	  EADDRINUSE },
+	/* ADDR_ANY vs specific EID, OK */
+	{ &bind_addrany_netdefault_type1, &bind_addr8_netdefault_type1, 0 },
+	/* ADDR_ANY different types, OK */
+	{ &bind_addrany_net2_type2, &bind_addrany_net2_type1, 0 },
+	/* ADDR_ANY different nets, OK */
+	{ &bind_addrany_net2_type1, &bind_addrany_netdefault_type1, 0 },
+
+	/* specific EID, NET_ANY (resolves to default)
+	 *  vs specific EID, explicit default net 1, conflict
+	 */
+	{ &bind_addr8_netdefault_type1, &bind_addr8_net1_type1, EADDRINUSE },
+
+	/* specific EID, net 1 vs specific EID, net 2, ok */
+	{ &bind_addr8_net1_type1, &bind_addr8_net2_type1, 0 },
+
+	/* ANY_ADDR, NET_ANY (doesn't resolve to default)
+	 *  vs ADDR_ANY, explicit default net 1, OK
+	 */
+	{ &bind_addrany_netdefault_type1, &bind_addrany_net1_type1, 0 },
+};
+
+static void mctp_bind_pair_desc(const struct mctp_bind_pair_test *t, char *desc)
+{
+	snprintf(desc, KUNIT_PARAM_DESC_SIZE,
+		 "{bind(addr %d, type %d, net %d)} {bind(addr %d, type %d, net %d)} -> error %d",
+		 t->bind1->bind_addr, t->bind1->bind_type, t->bind1->bind_net,
+		 t->bind2->bind_addr, t->bind2->bind_type, t->bind2->bind_net,
+		 t->error);
+}
+
+KUNIT_ARRAY_PARAM(mctp_bind_pair, mctp_bind_pair_tests, mctp_bind_pair_desc);
+
+static int
+mctp_test_bind_conflicts_inner(struct kunit *test,
+			       const struct mctp_test_bind_setup *bind1,
+			       const struct mctp_test_bind_setup *bind2)
+{
+	struct socket *sock1 = NULL, *sock2 = NULL, *sock3 = NULL;
+	int bind_errno;
+
+	/* Bind to first address, always succeeds */
+	mctp_test_bind_run(test, bind1, &bind_errno, &sock1);
+	KUNIT_EXPECT_EQ(test, bind_errno, 0);
+
+	/* A second identical bind always fails */
+	mctp_test_bind_run(test, bind1, &bind_errno, &sock2);
+	KUNIT_EXPECT_EQ(test, -bind_errno, EADDRINUSE);
+
+	/* A different bind, result is returned */
+	mctp_test_bind_run(test, bind2, &bind_errno, &sock3);
+
+	if (sock1)
+		sock_release(sock1);
+	if (sock2)
+		sock_release(sock2);
+	if (sock3)
+		sock_release(sock3);
+
+	return bind_errno;
+}
+
+static void mctp_test_bind_conflicts(struct kunit *test)
+{
+	const struct mctp_bind_pair_test *pair;
+	int bind_errno;
+
+	pair = test->param_value;
+
+	bind_errno =
+		mctp_test_bind_conflicts_inner(test, pair->bind1, pair->bind2);
+	KUNIT_EXPECT_EQ(test, -bind_errno, pair->error);
+
+	/* swapping the calls, the second bind should still fail */
+	bind_errno =
+		mctp_test_bind_conflicts_inner(test, pair->bind2, pair->bind1);
+	KUNIT_EXPECT_EQ(test, -bind_errno, pair->error);
+}
+
+static void mctp_test_assumptions(struct kunit *test)
+{
+	/* check assumption of default net from bind_addr8_net1_type1 */
+	KUNIT_ASSERT_EQ(test, mctp_default_net(&init_net), 1);
+}
+
 static struct kunit_case mctp_test_cases[] = {
+	KUNIT_CASE(mctp_test_assumptions),
 	KUNIT_CASE(mctp_test_sock_sendmsg_extaddr),
 	KUNIT_CASE(mctp_test_sock_recvmsg_extaddr),
+	KUNIT_CASE_PARAM(mctp_test_bind_conflicts, mctp_bind_pair_gen_params),
 	{}
 };
 
diff --git a/net/mctp/test/utils.c b/net/mctp/test/utils.c
index 01f5af416b814baf812b4352c513ffcdd9939cb2..c971e2c326f3564f95b3f693c450b3e6f3d9c594 100644
--- a/net/mctp/test/utils.c
+++ b/net/mctp/test/utils.c
@@ -258,3 +258,25 @@ struct sk_buff *__mctp_test_create_skb_data(const struct mctp_hdr *hdr,
 
 	return skb;
 }
+
+void mctp_test_bind_run(struct kunit *test,
+			const struct mctp_test_bind_setup *setup,
+			int *ret_bind_errno, struct socket **sock)
+{
+	struct sockaddr_mctp addr;
+	int rc;
+
+	*ret_bind_errno = -EIO;
+
+	rc = sock_create_kern(&init_net, AF_MCTP, SOCK_DGRAM, 0, sock);
+	KUNIT_ASSERT_EQ(test, rc, 0);
+
+	memset(&addr, 0x0, sizeof(addr));
+	addr.smctp_family = AF_MCTP;
+	addr.smctp_network = setup->bind_net;
+	addr.smctp_addr.s_addr = setup->bind_addr;
+	addr.smctp_type = setup->bind_type;
+
+	*ret_bind_errno =
+		kernel_bind(*sock, (struct sockaddr *)&addr, sizeof(addr));
+}
diff --git a/net/mctp/test/utils.h b/net/mctp/test/utils.h
index f10d1d9066ccde53bbaf471ea79b87b1d94cd755..7dd1a92ab770995db506c24dc805bb9e0839eeef 100644
--- a/net/mctp/test/utils.h
+++ b/net/mctp/test/utils.h
@@ -31,6 +31,12 @@ struct mctp_test_pktqueue {
 	struct sk_buff_head pkts;
 };
 
+struct mctp_test_bind_setup {
+	mctp_eid_t bind_addr;
+	int bind_net;
+	u8 bind_type;
+};
+
 struct mctp_test_dev *mctp_test_create_dev(void);
 struct mctp_test_dev *mctp_test_create_dev_lladdr(unsigned short lladdr_len,
 						  const unsigned char *lladdr);
@@ -61,4 +67,8 @@ struct sk_buff *__mctp_test_create_skb_data(const struct mctp_hdr *hdr,
 #define mctp_test_create_skb_data(h, d) \
 	__mctp_test_create_skb_data(h, d, sizeof(*d))
 
+void mctp_test_bind_run(struct kunit *test,
+			const struct mctp_test_bind_setup *setup,
+			int *ret_bind_errno, struct socket **sock);
+
 #endif /* __NET_MCTP_TEST_UTILS_H */

-- 
2.43.0

[PATCH net-next v3 5/8] net: mctp: Use hashtable for binds

[Matt Johnston]

Ensure that a specific EID (remote or local) bind will match in
preference to a MCTP_ADDR_ANY bind.

This adds infrastructure for binding a socket to receive messages from a
specific remote peer address, a future commit will expose an API for
this.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>

---
v2:
- Use DECLARE_HASHTABLE
- Fix long lines
---
 include/net/netns/mctp.h | 20 +++++++++---
 net/mctp/af_mctp.c       | 11 ++++---
 net/mctp/route.c         | 81 ++++++++++++++++++++++++++++++++++++++----------
 3 files changed, 87 insertions(+), 25 deletions(-)

diff --git a/include/net/netns/mctp.h b/include/net/netns/mctp.h
index 1db8f9aaddb4b96f4803df9f30a762f5f88d7f7f..89555f90b97b297e50a571b26c5232b824909da7 100644
--- a/include/net/netns/mctp.h
+++ b/include/net/netns/mctp.h
@@ -6,19 +6,25 @@
 #ifndef __NETNS_MCTP_H__
 #define __NETNS_MCTP_H__
 
+#include <linux/hash.h>
+#include <linux/hashtable.h>
 #include <linux/mutex.h>
 #include <linux/types.h>
 
+#define MCTP_BINDS_BITS 7
+
 struct netns_mctp {
 	/* Only updated under RTNL, entries freed via RCU */
 	struct list_head routes;
 
-	/* Bound sockets: list of sockets bound by type.
-	 * This list is updated from non-atomic contexts (under bind_lock),
-	 * and read (under rcu) in packet rx
+	/* Bound sockets: hash table of sockets, keyed by
+	 * (type, src_eid, dest_eid).
+	 * Specific src_eid/dest_eid entries also have an entry for
+	 * MCTP_ADDR_ANY. This list is updated from non-atomic contexts
+	 * (under bind_lock), and read (under rcu) in packet rx.
 	 */
 	struct mutex bind_lock;
-	struct hlist_head binds;
+	DECLARE_HASHTABLE(binds, MCTP_BINDS_BITS);
 
 	/* tag allocations. This list is read and updated from atomic contexts,
 	 * but elements are free()ed after a RCU grace-period
@@ -34,4 +40,10 @@ struct netns_mctp {
 	struct list_head neighbours;
 };
 
+static inline u32 mctp_bind_hash(u8 type, u8 local_addr, u8 peer_addr)
+{
+	return hash_32(type | (u32)local_addr << 8 | (u32)peer_addr << 16,
+		       MCTP_BINDS_BITS);
+}
+
 #endif /* __NETNS_MCTP_H__ */
diff --git a/net/mctp/af_mctp.c b/net/mctp/af_mctp.c
index 20edaf840a607700c04b740708763fbd02a2df47..16341de5cf2893bbc04a8c05a038c30be6570296 100644
--- a/net/mctp/af_mctp.c
+++ b/net/mctp/af_mctp.c
@@ -626,17 +626,17 @@ static int mctp_sk_hash(struct sock *sk)
 	struct net *net = sock_net(sk);
 	struct sock *existing;
 	struct mctp_sock *msk;
+	u32 hash;
 	int rc;
 
 	msk = container_of(sk, struct mctp_sock, sk);
 
-	/* Bind lookup runs under RCU, remain live during that. */
-	sock_set_flag(sk, SOCK_RCU_FREE);
+	hash = mctp_bind_hash(msk->bind_type, msk->bind_addr, MCTP_ADDR_ANY);
 
 	mutex_lock(&net->mctp.bind_lock);
 
 	/* Prevent duplicate binds. */
-	sk_for_each(existing, &net->mctp.binds) {
+	sk_for_each(existing, &net->mctp.binds[hash]) {
 		struct mctp_sock *mex =
 			container_of(existing, struct mctp_sock, sk);
 
@@ -648,7 +648,10 @@ static int mctp_sk_hash(struct sock *sk)
 		}
 	}
 
-	sk_add_node_rcu(sk, &net->mctp.binds);
+	/* Bind lookup runs under RCU, remain live during that. */
+	sock_set_flag(sk, SOCK_RCU_FREE);
+
+	sk_add_node_rcu(sk, &net->mctp.binds[hash]);
 	rc = 0;
 
 out:
diff --git a/net/mctp/route.c b/net/mctp/route.c
index a20d6b11d4186b55cab9d76e367169ea712553c7..69cfb0e6c545c2b44e5defdfac4e602c4f0265b1 100644
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -40,14 +40,45 @@ static int mctp_dst_discard(struct mctp_dst *dst, struct sk_buff *skb)
 	return 0;
 }
 
-static struct mctp_sock *mctp_lookup_bind(struct net *net, struct sk_buff *skb)
+static struct mctp_sock *mctp_lookup_bind_details(struct net *net,
+						  struct sk_buff *skb,
+						  u8 type, u8 dest,
+						  u8 src, bool allow_net_any)
 {
 	struct mctp_skb_cb *cb = mctp_cb(skb);
-	struct mctp_hdr *mh;
 	struct sock *sk;
-	u8 type;
+	u8 hash;
 
-	WARN_ON(!rcu_read_lock_held());
+	WARN_ON_ONCE(!rcu_read_lock_held());
+
+	hash = mctp_bind_hash(type, dest, src);
+
+	sk_for_each_rcu(sk, &net->mctp.binds[hash]) {
+		struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
+
+		if (!allow_net_any && msk->bind_net == MCTP_NET_ANY)
+			continue;
+
+		if (msk->bind_net != MCTP_NET_ANY && msk->bind_net != cb->net)
+			continue;
+
+		if (msk->bind_type != type)
+			continue;
+
+		if (!mctp_address_matches(msk->bind_addr, dest))
+			continue;
+
+		return msk;
+	}
+
+	return NULL;
+}
+
+static struct mctp_sock *mctp_lookup_bind(struct net *net, struct sk_buff *skb)
+{
+	struct mctp_sock *msk;
+	struct mctp_hdr *mh;
+	u8 type;
 
 	/* TODO: look up in skb->cb? */
 	mh = mctp_hdr(skb);
@@ -57,20 +88,36 @@ static struct mctp_sock *mctp_lookup_bind(struct net *net, struct sk_buff *skb)
 
 	type = (*(u8 *)skb->data) & 0x7f;
 
-	sk_for_each_rcu(sk, &net->mctp.binds) {
-		struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
-
-		if (msk->bind_net != MCTP_NET_ANY && msk->bind_net != cb->net)
-			continue;
-
-		if (msk->bind_type != type)
-			continue;
-
-		if (!mctp_address_matches(msk->bind_addr, mh->dest))
-			continue;
+	/* Look for binds in order of widening scope. A given destination or
+	 * source address also implies matching on a particular network.
+	 *
+	 * - Matching destination and source
+	 * - Matching destination
+	 * - Matching source
+	 * - Matching network, any address
+	 * - Any network or address
+	 */
 
+	msk = mctp_lookup_bind_details(net, skb, type, mh->dest, mh->src,
+				       false);
+	if (msk)
+		return msk;
+	msk = mctp_lookup_bind_details(net, skb, type, MCTP_ADDR_ANY, mh->src,
+				       false);
+	if (msk)
+		return msk;
+	msk = mctp_lookup_bind_details(net, skb, type, mh->dest, MCTP_ADDR_ANY,
+				       false);
+	if (msk)
+		return msk;
+	msk = mctp_lookup_bind_details(net, skb, type, MCTP_ADDR_ANY,
+				       MCTP_ADDR_ANY, false);
+	if (msk)
+		return msk;
+	msk = mctp_lookup_bind_details(net, skb, type, MCTP_ADDR_ANY,
+				       MCTP_ADDR_ANY, true);
+	if (msk)
 		return msk;
-	}
 
 	return NULL;
 }
@@ -1671,7 +1718,7 @@ static int __net_init mctp_routes_net_init(struct net *net)
 	struct netns_mctp *ns = &net->mctp;
 
 	INIT_LIST_HEAD(&ns->routes);
-	INIT_HLIST_HEAD(&ns->binds);
+	hash_init(ns->binds);
 	mutex_init(&ns->bind_lock);
 	INIT_HLIST_HEAD(&ns->keys);
 	spin_lock_init(&ns->keys_lock);

-- 
2.43.0

[PATCH net-next v3 6/8] net: mctp: Allow limiting binds to a peer address

[Matt Johnston]

Prior to calling bind() a program may call connect() on a socket to
restrict to a remote peer address.

Using connect() is the normal mechanism to specify a remote network
peer, so we use that here. In MCTP connect() is only used for bound
sockets - send() is not available for MCTP since a tag must be provided
for each message.

The smctp_type must match between connect() and bind() calls.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
---
 include/net/mctp.h |   5 ++-
 net/mctp/af_mctp.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++----
 net/mctp/route.c   |   6 +++-
 3 files changed, 106 insertions(+), 8 deletions(-)

diff --git a/include/net/mctp.h b/include/net/mctp.h
index ac4f4ecdfc24f1f481ff22a5673cb95e1bf21310..c3207ce98f07fcbb436e968d503bc45666794fdc 100644
--- a/include/net/mctp.h
+++ b/include/net/mctp.h
@@ -69,7 +69,10 @@ struct mctp_sock {
 
 	/* bind() params */
 	unsigned int	bind_net;
-	mctp_eid_t	bind_addr;
+	mctp_eid_t	bind_local_addr;
+	mctp_eid_t	bind_peer_addr;
+	unsigned int	bind_peer_net;
+	bool		bind_peer_set;
 	__u8		bind_type;
 
 	/* sendmsg()/recvmsg() uses struct sockaddr_mctp_ext */
diff --git a/net/mctp/af_mctp.c b/net/mctp/af_mctp.c
index 16341de5cf2893bbc04a8c05a038c30be6570296..79f3c53afebe4aafc14b710d8af2582e662b2df8 100644
--- a/net/mctp/af_mctp.c
+++ b/net/mctp/af_mctp.c
@@ -79,7 +79,7 @@ static int mctp_bind(struct socket *sock, struct sockaddr *addr, int addrlen)
 		goto out_release;
 	}
 
-	msk->bind_addr = smctp->smctp_addr.s_addr;
+	msk->bind_local_addr = smctp->smctp_addr.s_addr;
 
 	/* MCTP_NET_ANY with a specific EID is resolved to the default net
 	 * at bind() time.
@@ -87,13 +87,33 @@ static int mctp_bind(struct socket *sock, struct sockaddr *addr, int addrlen)
 	 * lookup time.
 	 */
 	if (smctp->smctp_network == MCTP_NET_ANY &&
-	    msk->bind_addr != MCTP_ADDR_ANY) {
+	    msk->bind_local_addr != MCTP_ADDR_ANY) {
 		msk->bind_net = mctp_default_net(net);
 	} else {
 		msk->bind_net = smctp->smctp_network;
 	}
 
-	msk->bind_type = smctp->smctp_type & 0x7f; /* ignore the IC bit */
+	/* ignore the IC bit */
+	smctp->smctp_type &= 0x7f;
+
+	if (msk->bind_peer_set) {
+		if (msk->bind_type != smctp->smctp_type) {
+			/* Prior connect() had a different type */
+			return -EINVAL;
+		}
+
+		if (msk->bind_net == MCTP_NET_ANY) {
+			/* Restrict to the network passed to connect() */
+			msk->bind_net = msk->bind_peer_net;
+		}
+
+		if (msk->bind_net != msk->bind_peer_net) {
+			/* connect() had a different net to bind() */
+			return -EINVAL;
+		}
+	} else {
+		msk->bind_type = smctp->smctp_type;
+	}
 
 	rc = sk->sk_prot->hash(sk);
 
@@ -103,6 +123,67 @@ static int mctp_bind(struct socket *sock, struct sockaddr *addr, int addrlen)
 	return rc;
 }
 
+/* Used to set a specific peer prior to bind. Not used for outbound
+ * connections (Tag Owner set) since MCTP is a datagram protocol.
+ */
+static int mctp_connect(struct socket *sock, struct sockaddr *addr,
+			int addrlen, int flags)
+{
+	struct sock *sk = sock->sk;
+	struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
+	struct net *net = sock_net(&msk->sk);
+	struct sockaddr_mctp *smctp;
+	int rc;
+
+	if (addrlen != sizeof(*smctp))
+		return -EINVAL;
+
+	if (addr->sa_family != AF_MCTP)
+		return -EAFNOSUPPORT;
+
+	/* It's a valid sockaddr for MCTP, cast and do protocol checks */
+	smctp = (struct sockaddr_mctp *)addr;
+
+	if (!mctp_sockaddr_is_ok(smctp))
+		return -EINVAL;
+
+	/* Can't bind by tag */
+	if (smctp->smctp_tag)
+		return -EINVAL;
+
+	/* IC bit must be unset */
+	if (smctp->smctp_type & 0x80)
+		return -EINVAL;
+
+	lock_sock(sk);
+
+	if (sk_hashed(sk)) {
+		/* bind() already */
+		rc = -EADDRINUSE;
+		goto out_release;
+	}
+
+	if (msk->bind_peer_set) {
+		/* connect() already */
+		rc = -EADDRINUSE;
+		goto out_release;
+	}
+
+	msk->bind_peer_set = true;
+	msk->bind_peer_addr = smctp->smctp_addr.s_addr;
+	msk->bind_type = smctp->smctp_type;
+	if (smctp->smctp_network == MCTP_NET_ANY)
+		msk->bind_peer_net = mctp_default_net(net);
+	else
+		msk->bind_peer_net = smctp->smctp_network;
+
+	rc = 0;
+
+out_release:
+	release_sock(sk);
+	return rc;
+}
+
 static int mctp_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
 {
 	DECLARE_SOCKADDR(struct sockaddr_mctp *, addr, msg->msg_name);
@@ -546,7 +627,7 @@ static const struct proto_ops mctp_dgram_ops = {
 	.family		= PF_MCTP,
 	.release	= mctp_release,
 	.bind		= mctp_bind,
-	.connect	= sock_no_connect,
+	.connect	= mctp_connect,
 	.socketpair	= sock_no_socketpair,
 	.accept		= sock_no_accept,
 	.getname	= sock_no_getname,
@@ -613,6 +694,7 @@ static int mctp_sk_init(struct sock *sk)
 
 	INIT_HLIST_HEAD(&msk->keys);
 	timer_setup(&msk->key_expiry, mctp_sk_expire_keys, 0);
+	msk->bind_peer_set = false;
 	return 0;
 }
 
@@ -626,12 +708,17 @@ static int mctp_sk_hash(struct sock *sk)
 	struct net *net = sock_net(sk);
 	struct sock *existing;
 	struct mctp_sock *msk;
+	mctp_eid_t remote;
 	u32 hash;
 	int rc;
 
 	msk = container_of(sk, struct mctp_sock, sk);
 
-	hash = mctp_bind_hash(msk->bind_type, msk->bind_addr, MCTP_ADDR_ANY);
+	if (msk->bind_peer_set)
+		remote = msk->bind_peer_addr;
+	else
+		remote = MCTP_ADDR_ANY;
+	hash = mctp_bind_hash(msk->bind_type, msk->bind_local_addr, remote);
 
 	mutex_lock(&net->mctp.bind_lock);
 
@@ -640,8 +727,12 @@ static int mctp_sk_hash(struct sock *sk)
 		struct mctp_sock *mex =
 			container_of(existing, struct mctp_sock, sk);
 
+		bool same_peer = (mex->bind_peer_set && msk->bind_peer_set &&
+				  mex->bind_peer_addr == msk->bind_peer_addr) ||
+				 (!mex->bind_peer_set && !msk->bind_peer_set);
+
 		if (mex->bind_type == msk->bind_type &&
-		    mex->bind_addr == msk->bind_addr &&
+		    mex->bind_local_addr == msk->bind_local_addr && same_peer &&
 		    mex->bind_net == msk->bind_net) {
 			rc = -EADDRINUSE;
 			goto out;
diff --git a/net/mctp/route.c b/net/mctp/route.c
index 69cfb0e6c545c2b44e5defdfac4e602c4f0265b1..2b2b958ef6a37525cc4d3f6a5758bd3880c98e6c 100644
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -65,7 +65,11 @@ static struct mctp_sock *mctp_lookup_bind_details(struct net *net,
 		if (msk->bind_type != type)
 			continue;
 
-		if (!mctp_address_matches(msk->bind_addr, dest))
+		if (msk->bind_peer_set &&
+		    !mctp_address_matches(msk->bind_peer_addr, src))
+			continue;
+
+		if (!mctp_address_matches(msk->bind_local_addr, dest))
 			continue;
 
 		return msk;

-- 
2.43.0

Re: [PATCH net-next v3 6/8] net: mctp: Allow limiting binds to a peer address

[Simon Horman]

On Wed, Jul 09, 2025 at 04:31:07PM +0800, Matt Johnston wrote:

...

> @@ -87,13 +87,33 @@ static int mctp_bind(struct socket *sock, struct sockaddr *addr, int addrlen)
>  	 * lookup time.
>  	 */
>  	if (smctp->smctp_network == MCTP_NET_ANY &&
> -	    msk->bind_addr != MCTP_ADDR_ANY) {
> +	    msk->bind_local_addr != MCTP_ADDR_ANY) {
>  		msk->bind_net = mctp_default_net(net);
>  	} else {
>  		msk->bind_net = smctp->smctp_network;
>  	}
>  
> -	msk->bind_type = smctp->smctp_type & 0x7f; /* ignore the IC bit */
> +	/* ignore the IC bit */
> +	smctp->smctp_type &= 0x7f;
> +
> +	if (msk->bind_peer_set) {
> +		if (msk->bind_type != smctp->smctp_type) {
> +			/* Prior connect() had a different type */
> +			return -EINVAL;

Hi Matt,

I think you need to set rc and goto out_release here so
that sk is released.

> +		}
> +
> +		if (msk->bind_net == MCTP_NET_ANY) {
> +			/* Restrict to the network passed to connect() */
> +			msk->bind_net = msk->bind_peer_net;
> +		}
> +
> +		if (msk->bind_net != msk->bind_peer_net) {
> +			/* connect() had a different net to bind() */
> +			return -EINVAL;

Ditto.

Flagged by Smatch.

> +		}
> +	} else {
> +		msk->bind_type = smctp->smctp_type;
> +	}
>  
>  	rc = sk->sk_prot->hash(sk);
>  

...

-- 
pw-bot: changes-requested

[PATCH net-next v3 7/8] net: mctp: Test conflicts of connect() with bind()

[Matt Johnston]

The addition of connect() adds new conflict cases to test.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>

---
v3:
- Moved test code to mctp/test/sock-test.c recently added in
  net-next
---
 net/mctp/test/sock-test.c | 45 +++++++++++++++++++++++++++++++++++++++++----
 net/mctp/test/utils.c     | 14 ++++++++++++++
 net/mctp/test/utils.h     |  4 ++++
 3 files changed, 59 insertions(+), 4 deletions(-)

diff --git a/net/mctp/test/sock-test.c b/net/mctp/test/sock-test.c
index 0cfc337be687e7ad903023d2fae9f12f75628532..b0942deb501980f196ce13da19ab171a3a9c9b8c 100644
--- a/net/mctp/test/sock-test.c
+++ b/net/mctp/test/sock-test.c
@@ -245,6 +245,11 @@ static const struct mctp_test_bind_setup bind_addrany_net2_type2 = {
 	.bind_addr = MCTP_ADDR_ANY, .bind_net = 2, .bind_type = 2,
 };
 
+static const struct mctp_test_bind_setup bind_addrany_net2_type1_peer9 = {
+	.bind_addr = MCTP_ADDR_ANY, .bind_net = 2, .bind_type = 1,
+	.have_peer = true, .peer_addr = 9, .peer_net = 2,
+};
+
 struct mctp_bind_pair_test {
 	const struct mctp_test_bind_setup *bind1;
 	const struct mctp_test_bind_setup *bind2;
@@ -278,19 +283,50 @@ static const struct mctp_bind_pair_test mctp_bind_pair_tests[] = {
 	 *  vs ADDR_ANY, explicit default net 1, OK
 	 */
 	{ &bind_addrany_netdefault_type1, &bind_addrany_net1_type1, 0 },
+
+	/* specific remote peer doesn't conflict with any-peer bind */
+	{ &bind_addrany_net2_type1_peer9, &bind_addrany_net2_type1, 0 },
+
+	/* bind() NET_ANY is allowed with a connect() net */
+	{ &bind_addrany_net2_type1_peer9, &bind_addrany_netdefault_type1, 0 },
 };
 
 static void mctp_bind_pair_desc(const struct mctp_bind_pair_test *t, char *desc)
 {
+	char peer1[25] = {0}, peer2[25] = {0};
+
+	if (t->bind1->have_peer)
+		snprintf(peer1, sizeof(peer1), ", peer %d net %d",
+			 t->bind1->peer_addr, t->bind1->peer_net);
+	if (t->bind2->have_peer)
+		snprintf(peer2, sizeof(peer2), ", peer %d net %d",
+			 t->bind2->peer_addr, t->bind2->peer_net);
+
 	snprintf(desc, KUNIT_PARAM_DESC_SIZE,
-		 "{bind(addr %d, type %d, net %d)} {bind(addr %d, type %d, net %d)} -> error %d",
-		 t->bind1->bind_addr, t->bind1->bind_type, t->bind1->bind_net,
-		 t->bind2->bind_addr, t->bind2->bind_type, t->bind2->bind_net,
-		 t->error);
+		 "{bind(addr %d, type %d, net %d%s)} {bind(addr %d, type %d, net %d%s)} -> error %d",
+		 t->bind1->bind_addr, t->bind1->bind_type,
+		 t->bind1->bind_net, peer1,
+		 t->bind2->bind_addr, t->bind2->bind_type,
+		 t->bind2->bind_net, peer2, t->error);
 }
 
 KUNIT_ARRAY_PARAM(mctp_bind_pair, mctp_bind_pair_tests, mctp_bind_pair_desc);
 
+static void mctp_test_bind_invalid(struct kunit *test)
+{
+	struct socket *sock;
+	int rc;
+
+	/* bind() fails if the bind() vs connect() networks mismatch. */
+	const struct mctp_test_bind_setup bind_connect_net_mismatch = {
+		.bind_addr = MCTP_ADDR_ANY, .bind_net = 1, .bind_type = 1,
+		.have_peer = true, .peer_addr = 9, .peer_net = 2,
+	};
+	mctp_test_bind_run(test, &bind_connect_net_mismatch, &rc, &sock);
+	KUNIT_EXPECT_EQ(test, -rc, EINVAL);
+	sock_release(sock);
+}
+
 static int
 mctp_test_bind_conflicts_inner(struct kunit *test,
 			       const struct mctp_test_bind_setup *bind1,
@@ -348,6 +384,7 @@ static struct kunit_case mctp_test_cases[] = {
 	KUNIT_CASE(mctp_test_sock_sendmsg_extaddr),
 	KUNIT_CASE(mctp_test_sock_recvmsg_extaddr),
 	KUNIT_CASE_PARAM(mctp_test_bind_conflicts, mctp_bind_pair_gen_params),
+	KUNIT_CASE(mctp_test_bind_invalid),
 	{}
 };
 
diff --git a/net/mctp/test/utils.c b/net/mctp/test/utils.c
index c971e2c326f3564f95b3f693c450b3e6f3d9c594..953d419027718959d913956c4c3893ef91624eb5 100644
--- a/net/mctp/test/utils.c
+++ b/net/mctp/test/utils.c
@@ -271,6 +271,20 @@ void mctp_test_bind_run(struct kunit *test,
 	rc = sock_create_kern(&init_net, AF_MCTP, SOCK_DGRAM, 0, sock);
 	KUNIT_ASSERT_EQ(test, rc, 0);
 
+	/* connect() if requested */
+	if (setup->have_peer) {
+		memset(&addr, 0x0, sizeof(addr));
+		addr.smctp_family = AF_MCTP;
+		addr.smctp_network = setup->peer_net;
+		addr.smctp_addr.s_addr = setup->peer_addr;
+		/* connect() type must match bind() type */
+		addr.smctp_type = setup->bind_type;
+		rc = kernel_connect(*sock, (struct sockaddr *)&addr,
+				    sizeof(addr), 0);
+		KUNIT_EXPECT_EQ(test, rc, 0);
+	}
+
+	/* bind() */
 	memset(&addr, 0x0, sizeof(addr));
 	addr.smctp_family = AF_MCTP;
 	addr.smctp_network = setup->bind_net;
diff --git a/net/mctp/test/utils.h b/net/mctp/test/utils.h
index 7dd1a92ab770995db506c24dc805bb9e0839eeef..c2aaba5188ab82237cb3bcc00d5abf1942753b9d 100644
--- a/net/mctp/test/utils.h
+++ b/net/mctp/test/utils.h
@@ -35,6 +35,10 @@ struct mctp_test_bind_setup {
 	mctp_eid_t bind_addr;
 	int bind_net;
 	u8 bind_type;
+
+	bool have_peer;
+	mctp_eid_t peer_addr;
+	int peer_net;
 };
 
 struct mctp_test_dev *mctp_test_create_dev(void);

-- 
2.43.0

[PATCH net-next v3 8/8] net: mctp: Add bind lookup test

[Matt Johnston]

Test the preference order of bound socket matches with a series of test
packets.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>

---
v3:
- Updated test code for changes from net-next
---
 net/mctp/test/route-test.c | 188 +++++++++++++++++++++++++++++++++++++++++++++
 net/mctp/test/utils.h      |   3 +
 2 files changed, 191 insertions(+)

diff --git a/net/mctp/test/route-test.c b/net/mctp/test/route-test.c
index 12811032a2696167b4f319cbc9c81fef4cb2d951..fb6b46a952cb432163f6adb40bb395d658745efd 100644
--- a/net/mctp/test/route-test.c
+++ b/net/mctp/test/route-test.c
@@ -1408,6 +1408,193 @@ static void mctp_test_route_gw_output(struct kunit *test)
 	kfree_skb(skb);
 }
 
+struct mctp_bind_lookup_test {
+	/* header of incoming message */
+	struct mctp_hdr hdr;
+	u8 ty;
+	/* mctp network of incoming interface (smctp_network) */
+	unsigned int net;
+
+	/* expected socket, matches .name in lookup_binds, NULL for dropped */
+	const char *expect;
+};
+
+/* Single-packet TO-set message */
+#define LK(src, dst) RX_HDR(1, (src), (dst), FL_S | FL_E | FL_TO)
+
+/* Input message test cases for bind lookup tests.
+ *
+ * 10 and 11 are local EIDs.
+ * 20 and 21 are remote EIDs.
+ */
+static const struct mctp_bind_lookup_test mctp_bind_lookup_tests[] = {
+	/* both local-eid and remote-eid binds, remote eid is preferenced */
+	{ .hdr = LK(20, 10),  .ty = 1, .net = 1, .expect = "remote20" },
+
+	{ .hdr = LK(20, 255), .ty = 1, .net = 1, .expect = "remote20" },
+	{ .hdr = LK(20, 0),   .ty = 1, .net = 1, .expect = "remote20" },
+	{ .hdr = LK(0, 255),  .ty = 1, .net = 1, .expect = "any" },
+	{ .hdr = LK(0, 11),   .ty = 1, .net = 1, .expect = "any" },
+	{ .hdr = LK(0, 0),    .ty = 1, .net = 1, .expect = "any" },
+	{ .hdr = LK(0, 10),   .ty = 1, .net = 1, .expect = "local10" },
+	{ .hdr = LK(21, 10),  .ty = 1, .net = 1, .expect = "local10" },
+	{ .hdr = LK(21, 11),  .ty = 1, .net = 1, .expect = "remote21local11" },
+
+	/* both src and dest set to eid=99. unusual, but accepted
+	 * by MCTP stack currently.
+	 */
+	{ .hdr = LK(99, 99),  .ty = 1, .net = 1, .expect = "any" },
+
+	/* unbound smctp_type */
+	{ .hdr = LK(20, 10),  .ty = 3, .net = 1, .expect = NULL },
+
+	/* smctp_network tests */
+
+	{ .hdr = LK(0, 0),    .ty = 1, .net = 7, .expect = "any" },
+	{ .hdr = LK(21, 10),  .ty = 1, .net = 2, .expect = "any" },
+
+	/* remote EID 20 matches, but MCTP_NET_ANY in "remote20" resolved
+	 * to net=1, so lookup doesn't match "remote20"
+	 */
+	{ .hdr = LK(20, 10),  .ty = 1, .net = 3, .expect = "any" },
+
+	{ .hdr = LK(21, 10),  .ty = 1, .net = 3, .expect = "remote21net3" },
+	{ .hdr = LK(21, 10),  .ty = 1, .net = 4, .expect = "remote21net4" },
+	{ .hdr = LK(21, 10),  .ty = 1, .net = 5, .expect = "remote21net5" },
+
+	{ .hdr = LK(21, 10),  .ty = 1, .net = 5, .expect = "remote21net5" },
+
+	{ .hdr = LK(99, 10),  .ty = 1, .net = 8, .expect = "local10net8" },
+
+	{ .hdr = LK(99, 10),  .ty = 1, .net = 9, .expect = "anynet9" },
+	{ .hdr = LK(0, 0),    .ty = 1, .net = 9, .expect = "anynet9" },
+	{ .hdr = LK(99, 99),  .ty = 1, .net = 9, .expect = "anynet9" },
+	{ .hdr = LK(20, 10),  .ty = 1, .net = 9, .expect = "anynet9" },
+};
+
+/* Binds to create during the lookup tests */
+static const struct mctp_test_bind_setup lookup_binds[] = {
+	/* any address and net, type 1 */
+	{ .name = "any", .bind_addr = MCTP_ADDR_ANY,
+		.bind_net = MCTP_NET_ANY, .bind_type = 1, },
+	/* local eid 10, net 1 (resolved from MCTP_NET_ANY) */
+	{ .name = "local10", .bind_addr = 10,
+		.bind_net = MCTP_NET_ANY, .bind_type = 1, },
+	/* local eid 10, net 8 */
+	{ .name = "local10net8", .bind_addr = 10,
+		.bind_net = 8, .bind_type = 1, },
+	/* any EID, net 9 */
+	{ .name = "anynet9", .bind_addr = MCTP_ADDR_ANY,
+		.bind_net = 9, .bind_type = 1, },
+
+	/* remote eid 20, net 1, any local eid */
+	{ .name = "remote20", .bind_addr = MCTP_ADDR_ANY,
+		.bind_net = MCTP_NET_ANY, .bind_type = 1,
+		.have_peer = true, .peer_addr = 20, .peer_net = MCTP_NET_ANY, },
+
+	/* remote eid 20, net 1, local eid 11 */
+	{ .name = "remote21local11", .bind_addr = 11,
+		.bind_net = MCTP_NET_ANY, .bind_type = 1,
+		.have_peer = true, .peer_addr = 21, .peer_net = MCTP_NET_ANY, },
+
+	/* remote eid 21, specific net=3 for connect() */
+	{ .name = "remote21net3", .bind_addr = MCTP_ADDR_ANY,
+		.bind_net = MCTP_NET_ANY, .bind_type = 1,
+		.have_peer = true, .peer_addr = 21, .peer_net = 3, },
+
+	/* remote eid 21, net 4 for bind, specific net=4 for connect() */
+	{ .name = "remote21net4", .bind_addr = MCTP_ADDR_ANY,
+		.bind_net = 4, .bind_type = 1,
+		.have_peer = true, .peer_addr = 21, .peer_net = 4, },
+
+	/* remote eid 21, net 5 for bind, specific net=5 for connect() */
+	{ .name = "remote21net5", .bind_addr = MCTP_ADDR_ANY,
+		.bind_net = 5, .bind_type = 1,
+		.have_peer = true, .peer_addr = 21, .peer_net = 5, },
+};
+
+static void mctp_bind_lookup_desc(const struct mctp_bind_lookup_test *t,
+				  char *desc)
+{
+	snprintf(desc, KUNIT_PARAM_DESC_SIZE,
+		 "{src %d dst %d ty %d net %d expect %s}",
+		 t->hdr.src, t->hdr.dest, t->ty, t->net, t->expect);
+}
+
+KUNIT_ARRAY_PARAM(mctp_bind_lookup, mctp_bind_lookup_tests,
+		  mctp_bind_lookup_desc);
+
+static void mctp_test_bind_lookup(struct kunit *test)
+{
+	const struct mctp_bind_lookup_test *rx;
+	struct socket *socks[ARRAY_SIZE(lookup_binds)];
+	struct sk_buff *skb_pkt = NULL, *skb_sock = NULL;
+	struct socket *sock_ty0, *sock_expect = NULL;
+	struct mctp_test_pktqueue tpq;
+	struct mctp_test_dev *dev;
+	struct mctp_dst dst;
+	int rc;
+
+	rx = test->param_value;
+
+	__mctp_route_test_init(test, &dev, &dst, &tpq, &sock_ty0, rx->net);
+	/* Create all binds */
+	for (size_t i = 0; i < ARRAY_SIZE(lookup_binds); i++) {
+		mctp_test_bind_run(test, &lookup_binds[i],
+				   &rc, &socks[i]);
+		KUNIT_ASSERT_EQ(test, rc, 0);
+
+		/* Record the expected receive socket */
+		if (rx->expect &&
+		    strcmp(rx->expect, lookup_binds[i].name) == 0) {
+			KUNIT_ASSERT_NULL(test, sock_expect);
+			sock_expect = socks[i];
+		}
+	}
+	KUNIT_ASSERT_EQ(test, !!sock_expect, !!rx->expect);
+
+	/* Create test message */
+	skb_pkt = mctp_test_create_skb_data(&rx->hdr, &rx->ty);
+	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, skb_pkt);
+	mctp_test_skb_set_dev(skb_pkt, dev);
+	mctp_test_pktqueue_init(&tpq);
+
+	rc = mctp_dst_input(&dst, skb_pkt);
+	if (rx->expect) {
+		/* Test the message is received on the expected socket */
+		KUNIT_EXPECT_EQ(test, rc, 0);
+		skb_sock = skb_recv_datagram(sock_expect->sk,
+					     MSG_DONTWAIT, &rc);
+		if (!skb_sock) {
+			/* Find which socket received it instead */
+			for (size_t i = 0; i < ARRAY_SIZE(lookup_binds); i++) {
+				skb_sock = skb_recv_datagram(socks[i]->sk,
+							     MSG_DONTWAIT, &rc);
+				if (skb_sock) {
+					KUNIT_FAIL(test,
+						   "received on incorrect socket '%s', expect '%s'",
+						   lookup_binds[i].name,
+						   rx->expect);
+					goto cleanup;
+				}
+			}
+			KUNIT_FAIL(test, "no message received");
+		}
+	} else {
+		KUNIT_EXPECT_NE(test, rc, 0);
+	}
+
+cleanup:
+	kfree_skb(skb_sock);
+	kfree_skb(skb_pkt);
+
+	/* Drop all binds */
+	for (size_t i = 0; i < ARRAY_SIZE(lookup_binds); i++)
+		sock_release(socks[i]);
+
+	__mctp_route_test_fini(test, dev, &dst, &tpq, sock_ty0);
+}
+
 static struct kunit_case mctp_test_cases[] = {
 	KUNIT_CASE_PARAM(mctp_test_fragment, mctp_frag_gen_params),
 	KUNIT_CASE_PARAM(mctp_test_rx_input, mctp_rx_input_gen_params),
@@ -1429,6 +1616,7 @@ static struct kunit_case mctp_test_cases[] = {
 	KUNIT_CASE(mctp_test_route_gw_loop),
 	KUNIT_CASE_PARAM(mctp_test_route_gw_mtu, mctp_route_gw_mtu_gen_params),
 	KUNIT_CASE(mctp_test_route_gw_output),
+	KUNIT_CASE_PARAM(mctp_test_bind_lookup, mctp_bind_lookup_gen_params),
 	{}
 };
 
diff --git a/net/mctp/test/utils.h b/net/mctp/test/utils.h
index c2aaba5188ab82237cb3bcc00d5abf1942753b9d..06bdb6cb5eff6560c7378cf37a1bb17757938e82 100644
--- a/net/mctp/test/utils.h
+++ b/net/mctp/test/utils.h
@@ -39,6 +39,9 @@ struct mctp_test_bind_setup {
 	bool have_peer;
 	mctp_eid_t peer_addr;
 	int peer_net;
+
+	/* optional name. Used for comparison in "lookup" tests */
+	const char *name;
 };
 
 struct mctp_test_dev *mctp_test_create_dev(void);

-- 
2.43.0