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Message-Id: <20250709-mctp-bind-v3-6-eac98bbf5e95@codeconstruct.com.au>
Date: Wed, 09 Jul 2025 16:31:07 +0800
From: Matt Johnston <matt@...econstruct.com.au>
To: Jeremy Kerr <jk@...econstruct.com.au>,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>
Cc: netdev@...r.kernel.org, Matt Johnston <matt@...econstruct.com.au>
Subject: [PATCH net-next v3 6/8] net: mctp: Allow limiting binds to a peer
address
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@...econstruct.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
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