* [PATCH can-next v3 1/3] af_can: ensure sk_protocol is always set on socket creation
2026-09-04 14:12 [PATCH can-next v3 0/3] Introduce diag support for CAN Filippo Storniolo
@ 2026-09-04 14:12 ` Filippo Storniolo
2026-09-04 14:12 ` [PATCH can-next v3 2/3] af_can: store socket pointers in struct netns_can Filippo Storniolo
2026-09-04 14:12 ` [PATCH can-next v3 3/3] can: add can diag interface Filippo Storniolo
2 siblings, 0 replies; 5+ messages in thread
From: Filippo Storniolo @ 2026-09-04 14:12 UTC (permalink / raw)
To: Oliver Hartkopp, Marc Kleine-Budde, Robin van der Gracht,
Oleksij Rempel, kernel, Urs Thuermann, Paolo Abeni, Simon Horman
Cc: linux-can, Davide Caratti
From: Davide Caratti <dcaratti@redhat.com>
Currently, only j1939 assigns a value to 'sk_protocol'. As a prerequisite
for the implementation of CAN sockets diagnostics, AF_CAN sockets need an
easy way to determine which protocol is on top of an existing socket.
POC test using can-tests:
| # perf probe -m can_j1939 --add "j1939_sk_recvmsg sock->sk->sk_protocol"
| # perf record -e probe:j1939_sk_recvmsg -aR -- ./j1939/tst-j1939-ac
| [...]
| # perf script
| tst-j1939-ac 5807 [002] 322767.312599: probe:j1939_sk_recvmsg: (ffffffffc0b29a14) sk_protocol=0x7
| ^^^ 0x7, that's CAN_J1939
| # perf probe -m can_raw --add "raw_recvmsg sock->sk->sk_protocol"
| # perf record -e probe:raw_recvmsg -aR ./netlayer/tst-rcv-own-msgs vcan0
| # perf script
| [...]
| tst-rcv-own-msg 5816 [001] 323173.651122: probe:raw_recvmsg: (ffffffffc0b20154) sk_protocol=0x1
| ^^^ 0x1, that's CAN_RAW. It was 0x0 on unpatched kernel
Storing the "protocol" value in can_create() fixes the problem. This also
fixes AF_CAN support for the following system call:
| getsockopt(..., SOL_SOCKET, SO_PROTOCOL, &proto, sizeof(proto))
that was assigning 0 to 'proto' since the earliest kernel versions.
Fixes: 0d66548a10cb ("[CAN]: Add PF_CAN core module")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
---
net/can/af_can.c | 1 +
net/can/j1939/socket.c | 1 -
2 files changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 7bc86b176b4d..65af25946985 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -162,6 +162,7 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
}
sock_init_data(sock, sk);
+ sk->sk_protocol = protocol;
sk->sk_destruct = can_sock_destruct;
if (sk->sk_prot->init)
diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index 50a598ef5fd4..ccd43ff5519c 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -420,7 +420,6 @@ static int j1939_sk_init(struct sock *sk)
/* j1939_sk_sock_destruct() depends on SOCK_RCU_FREE flag */
sock_set_flag(sk, SOCK_RCU_FREE);
sk->sk_destruct = j1939_sk_sock_destruct;
- sk->sk_protocol = CAN_J1939;
return 0;
}
--
2.55.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH can-next v3 2/3] af_can: store socket pointers in struct netns_can
2026-09-04 14:12 [PATCH can-next v3 0/3] Introduce diag support for CAN Filippo Storniolo
2026-09-04 14:12 ` [PATCH can-next v3 1/3] af_can: ensure sk_protocol is always set on socket creation Filippo Storniolo
@ 2026-09-04 14:12 ` Filippo Storniolo
2026-09-04 14:12 ` [PATCH can-next v3 3/3] can: add can diag interface Filippo Storniolo
2 siblings, 0 replies; 5+ messages in thread
From: Filippo Storniolo @ 2026-09-04 14:12 UTC (permalink / raw)
To: Oliver Hartkopp, Marc Kleine-Budde, Robin van der Gracht,
Oleksij Rempel, kernel, Urs Thuermann, Paolo Abeni, Simon Horman
Cc: linux-can, Filippo Storniolo
AF_CAN sockets need to be stored in the netns_can structure
in order to be retrieved by the CAN diagnostic module when
a netlink request message is issued by the userspace.
On socket creation (`can_create()`), add the pointer to the
new socket to `netns_can::sk_list`. During socket release
(`isotp_release()`, `raw_release()`, `j1939_release()`,
`bcm_release()`), remove the corresponding pointer from
this list.
Since this is a prerequisite of the CAN diagnostic module,
deletes and insert operations are conditioned by
IS_ENABLED(CONFIG_CAN_DIAG).
Signed-off-by: Filippo Storniolo <fstornio@redhat.com>
---
include/linux/can/core.h | 11 +++++++++++
include/net/netns/can.h | 6 ++++++
net/can/af_can.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++
net/can/bcm.c | 2 ++
net/can/isotp.c | 2 ++
net/can/j1939/socket.c | 2 ++
net/can/raw.c | 2 ++
7 files changed, 75 insertions(+)
diff --git a/include/linux/can/core.h b/include/linux/can/core.h
index 3287232e3cad..75d9139f33fb 100644
--- a/include/linux/can/core.h
+++ b/include/linux/can/core.h
@@ -61,4 +61,15 @@ extern int can_send(struct sk_buff *skb, int loop);
void can_set_skb_uid(struct sk_buff *skb);
void can_sock_destruct(struct sock *sk);
+/* function prototypes for the CAN diag module */
+#if IS_ENABLED(CONFIG_CAN_DIAG)
+void lock_can_diag_mutex(struct net *net);
+void unlock_can_diag_mutex(struct net *net);
+void can_add_sock_sklist(struct sock *sk);
+void can_remove_sock_sklist(struct sock *sk);
+#else
+static inline void can_add_sock_sklist(struct sock *sk) {};
+static inline void can_remove_sock_sklist(struct sock *sk) {};
+#endif
+
#endif /* !_CAN_CORE_H */
diff --git a/include/net/netns/can.h b/include/net/netns/can.h
index 48b79f7e6236..d60273d8a95d 100644
--- a/include/net/netns/can.h
+++ b/include/net/netns/can.h
@@ -36,6 +36,12 @@ struct netns_can {
/* CAN GW per-net gateway jobs */
struct hlist_head cgw_list;
+
+#if IS_ENABLED(CONFIG_CAN_DIAG)
+ /* CAN diag support */
+ struct mutex sklist_lock;
+ struct hlist_head sklist;
+#endif
};
#endif /* __NETNS_CAN_H__ */
diff --git a/net/can/af_can.c b/net/can/af_can.c
index 65af25946985..1ea36411f219 100644
--- a/net/can/af_can.c
+++ b/net/can/af_can.c
@@ -111,6 +111,44 @@ static inline void can_put_proto(const struct can_proto *cp)
module_put(cp->prot->owner);
}
+#if IS_ENABLED(CONFIG_CAN_DIAG)
+void lock_can_diag_mutex(struct net *net)
+{
+ mutex_lock(&net->can.sklist_lock);
+}
+EXPORT_SYMBOL(lock_can_diag_mutex);
+
+void unlock_can_diag_mutex(struct net *net)
+{
+ mutex_unlock(&net->can.sklist_lock);
+}
+EXPORT_SYMBOL(unlock_can_diag_mutex);
+
+void can_add_sock_sklist(struct sock *sk)
+{
+ struct net *net;
+
+ net = sock_net(sk);
+
+ lock_can_diag_mutex(net);
+ sk_add_node(sk, &net->can.sklist);
+ unlock_can_diag_mutex(net);
+}
+EXPORT_SYMBOL(can_add_sock_sklist);
+
+void can_remove_sock_sklist(struct sock *sk)
+{
+ struct net *net;
+
+ net = sock_net(sk);
+
+ lock_can_diag_mutex(net);
+ sk_del_node_init(sk);
+ unlock_can_diag_mutex(net);
+}
+EXPORT_SYMBOL(can_remove_sock_sklist);
+#endif
+
static int can_create(struct net *net, struct socket *sock, int protocol,
int kern)
{
@@ -174,6 +212,8 @@ static int can_create(struct net *net, struct socket *sock, int protocol,
sock_put(sk);
sock->sk = NULL;
} else {
+ can_add_sock_sklist(sk);
+
sock_prot_inuse_add(net, sk->sk_prot, 1);
}
@@ -799,6 +839,12 @@ EXPORT_SYMBOL(can_proto_unregister);
static int can_pernet_init(struct net *net)
{
spin_lock_init(&net->can.rcvlists_lock);
+
+#if IS_ENABLED(CONFIG_CAN_DIAG)
+ mutex_init(&net->can.sklist_lock);
+ INIT_HLIST_HEAD(&net->can.sklist);
+#endif
+
net->can.rx_alldev_list = kzalloc_obj(*net->can.rx_alldev_list);
if (!net->can.rx_alldev_list)
goto out;
@@ -842,6 +888,10 @@ static void can_pernet_exit(struct net *net)
kfree(net->can.rx_alldev_list);
kfree(net->can.pkg_stats);
kfree(net->can.rcv_lists_stats);
+
+#if IS_ENABLED(CONFIG_CAN_DIAG)
+ WARN_ON_ONCE(!hlist_empty(&net->can.sklist));
+#endif
}
/* af_can module init/exit functions */
diff --git a/net/can/bcm.c b/net/can/bcm.c
index 3d637a1e0ac1..a90b7aea2869 100644
--- a/net/can/bcm.c
+++ b/net/can/bcm.c
@@ -1921,6 +1921,8 @@ static int bcm_release(struct socket *sock)
if (!sk)
return 0;
+ can_remove_sock_sklist(sk);
+
net = sock_net(sk);
bo = bcm_sk(sk);
diff --git a/net/can/isotp.c b/net/can/isotp.c
index 155530aedce2..25098c5546d2 100644
--- a/net/can/isotp.c
+++ b/net/can/isotp.c
@@ -1455,6 +1455,8 @@ static int isotp_release(struct socket *sock)
so = isotp_sk(sk);
net = sock_net(sk);
+ can_remove_sock_sklist(sk);
+
/* best-effort: wait for a running pdu to finish, but don't block on
* it forever - give up after the first signal
*/
diff --git a/net/can/j1939/socket.c b/net/can/j1939/socket.c
index ccd43ff5519c..cbfd0b888768 100644
--- a/net/can/j1939/socket.c
+++ b/net/can/j1939/socket.c
@@ -641,6 +641,8 @@ static int j1939_sk_release(struct socket *sock)
if (!sk)
return 0;
+ can_remove_sock_sklist(sk);
+
lock_sock(sk);
jsk = j1939_sk(sk);
diff --git a/net/can/raw.c b/net/can/raw.c
index 82d9c0499c95..7784b8fd8d19 100644
--- a/net/can/raw.c
+++ b/net/can/raw.c
@@ -418,6 +418,8 @@ static int raw_release(struct socket *sock)
ro = raw_sk(sk);
net = sock_net(sk);
+ can_remove_sock_sklist(sk);
+
spin_lock(&raw_notifier_lock);
while (raw_busy_notifier == ro) {
spin_unlock(&raw_notifier_lock);
--
2.55.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* [PATCH can-next v3 3/3] can: add can diag interface
2026-09-04 14:12 [PATCH can-next v3 0/3] Introduce diag support for CAN Filippo Storniolo
2026-09-04 14:12 ` [PATCH can-next v3 1/3] af_can: ensure sk_protocol is always set on socket creation Filippo Storniolo
2026-09-04 14:12 ` [PATCH can-next v3 2/3] af_can: store socket pointers in struct netns_can Filippo Storniolo
@ 2026-09-04 14:12 ` Filippo Storniolo
2026-09-04 14:26 ` sashiko-bot
2 siblings, 1 reply; 5+ messages in thread
From: Filippo Storniolo @ 2026-09-04 14:12 UTC (permalink / raw)
To: Oliver Hartkopp, Marc Kleine-Budde, Robin van der Gracht,
Oleksij Rempel, kernel, Urs Thuermann, Paolo Abeni, Simon Horman
Cc: linux-can, Davide Caratti, Filippo Storniolo
Add the can_diag interface for querying sockets from userspace.
ss(8) tool can use this interface to list open sockets.
The userspace ABI is defined in <linux/can/diag.h> and includes
netlink request and response structs. The request queries open
can sockets and the response contains socket information fields
including the interface index for bound sockets, inode number,
transport protocol etc.
Support can be added later by extending can_diag_dump().
Suggested-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: Filippo Storniolo <fstornio@redhat.com>
---
MAINTAINERS | 1 +
include/uapi/linux/can/diag.h | 50 +++++++++++
net/can/Kconfig | 10 +++
net/can/Makefile | 3 +
net/can/diag.c | 203 ++++++++++++++++++++++++++++++++++++++++++
5 files changed, 267 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS
index b23fb6f2f4ef..c718d7477fa7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5859,6 +5859,7 @@ F: include/net/can.h
F: include/net/netns/can.h
F: include/uapi/linux/can.h
F: include/uapi/linux/can/bcm.h
+F: include/uapi/linux/can/diag.h
F: include/uapi/linux/can/gw.h
F: include/uapi/linux/can/isotp.h
F: include/uapi/linux/can/raw.h
diff --git a/include/uapi/linux/can/diag.h b/include/uapi/linux/can/diag.h
new file mode 100644
index 000000000000..f22103e7bf90
--- /dev/null
+++ b/include/uapi/linux/can/diag.h
@@ -0,0 +1,50 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+
+#ifndef _UAPI_CAN_DIAG_H_
+#define _UAPI_CAN_DIAG_H_
+
+#include <linux/types.h>
+#include <linux/can.h>
+#include <linux/const.h>
+
+/* Request */
+struct can_diag_req {
+ __u8 sdiag_family; /* must be AF_CAN */
+ __u8 pad;
+ __u16 sdiag_protocol; /* for future filtering of transport protocols */
+ __u32 cdiag_states;
+ __u32 cdiag_ino;
+ __u32 cdiag_show;
+ __u32 cdiag_cookie[2];
+};
+
+#define CDIAG_SHOW_UID _BITUL(0) /* show socket's UID */
+
+enum {
+ CAN_DIAG_UNSPEC,
+ CAN_DIAG_UID,
+ CAN_DIAG_ISOTP_TX_ID,
+ CAN_DIAG_ISOTP_RX_ID,
+ CAN_DIAG_J1939_NAME,
+ CAN_DIAG_J1939_PGN,
+ CAN_DIAG_J1939_ADDR,
+
+ __CAN_DIAG_MAX,
+};
+
+#define CAN_DIAG_MAX (__CAN_DIAG_MAX - 1)
+
+/* Response */
+struct can_diag_msg {
+ __u8 cdiag_family; /* AF_CAN */
+ __u8 cdiag_state;
+ __u16 cdiag_protocol;
+ __u16 cdiag_type;
+ __u16 pad16;
+ __u32 cdiag_cookie[2];
+ __s32 cdiag_ifindex;
+ __u32 pad32;
+ __u64 cdiag_ino;
+};
+
+#endif /* _UAPI_CAN_DIAG_H_ */
diff --git a/net/can/Kconfig b/net/can/Kconfig
index abbb4be7ad21..bbab2c70326b 100644
--- a/net/can/Kconfig
+++ b/net/can/Kconfig
@@ -70,4 +70,14 @@ config CAN_ISOTP
as needed e.g. for vehicle diagnosis (UDS, ISO 14229) or IP-over-CAN
traffic.
+config CAN_DIAG
+ tristate "CAN socket monitoring interface"
+ depends on CAN
+ default m
+ help
+ Support for CAN socket monitoring interface used by the ss tool.
+ If unsure, say M.
+
+ Enable this module so userspace applications can query open sockets.
+
endif
diff --git a/net/can/Makefile b/net/can/Makefile
index 58f2c31c1ef3..c0ddeb9a012c 100644
--- a/net/can/Makefile
+++ b/net/can/Makefile
@@ -20,3 +20,6 @@ obj-$(CONFIG_CAN_J1939) += j1939/
obj-$(CONFIG_CAN_ISOTP) += can-isotp.o
can-isotp-y := isotp.o
+
+obj-$(CONFIG_CAN_DIAG) += can-diag.o
+can-diag-y := diag.o
diff --git a/net/can/diag.c b/net/can/diag.c
new file mode 100644
index 000000000000..647a94636a54
--- /dev/null
+++ b/net/can/diag.c
@@ -0,0 +1,203 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *
+ * Copyright (C) 2026 Red Hat
+ * Author: Filippo Storniolo <fstornio@redhat.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/net.h>
+#include <net/netlink.h>
+#include <linux/sock_diag.h>
+#include <linux/can.h>
+#include <linux/can/diag.h>
+#include <net/net_namespace.h>
+#include <net/sock.h>
+#include <linux/netdevice.h>
+#include <linux/user_namespace.h>
+#include <linux/can/core.h>
+
+static int sk_diag_dump_uid(struct sock *sk, struct sk_buff *skb,
+ struct user_namespace *user_ns)
+{
+ uid_t uid = from_kuid_munged(user_ns, sk_uid(sk));
+
+ return nla_put(skb, CAN_DIAG_UID, sizeof(uid_t), &uid);
+}
+
+static int sk_diag_fill(struct sock *sk, struct sk_buff *skb,
+ struct can_diag_req *req, /* will be used for filtering */
+ struct user_namespace *user_ns,
+ u32 portid, u32 seq, u32 flags, u64 sk_ino)
+{
+ struct sockaddr_can can_addr;
+ struct can_diag_msg *rep;
+ struct nlmsghdr *nlh;
+ int err;
+
+ nlh = nlmsg_put(skb, portid, seq, SOCK_DIAG_BY_FAMILY, sizeof(*rep), flags);
+ if (!nlh)
+ return -EMSGSIZE;
+
+ rep = nlmsg_data(nlh);
+ memset(rep, 0, sizeof(struct can_diag_msg));
+
+ rep->cdiag_family = AF_CAN;
+ rep->cdiag_type = sk->sk_type;
+ rep->cdiag_ino = sk_ino;
+ rep->cdiag_protocol = sk->sk_protocol;
+ rep->cdiag_state = READ_ONCE(sk->sk_state);
+ sock_diag_save_cookie(sk, rep->cdiag_cookie);
+
+ if ((req->cdiag_show & CDIAG_SHOW_UID)) {
+ err = sk_diag_dump_uid(sk, skb, user_ns);
+ if (err < 0)
+ goto cancel_nlmsg_err;
+ }
+
+ memset(&can_addr, 0, sizeof(can_addr));
+
+ err = kernel_getsockname(sk->sk_socket, (struct sockaddr *)&can_addr);
+ if (err < 0) {
+ /* Some protocols (e.g. CAN_BCM) do not implement kernel_getsockname().
+ * No error returned because the netlink message is still valid.
+ */
+ if (err == -EOPNOTSUPP)
+ goto exit_no_err;
+
+ goto cancel_nlmsg_err;
+ }
+
+ rep->cdiag_ifindex = can_addr.can_ifindex;
+
+ switch (sk->sk_protocol) {
+ case CAN_ISOTP:
+ {
+ canid_t tx_id;
+ canid_t rx_id;
+
+ tx_id = can_addr.can_addr.tp.tx_id;
+ rx_id = can_addr.can_addr.tp.rx_id;
+
+ err = nla_put(skb, CAN_DIAG_ISOTP_TX_ID, sizeof(canid_t), &tx_id);
+ if (err < 0)
+ goto cancel_nlmsg_err;
+
+ err = nla_put(skb, CAN_DIAG_ISOTP_RX_ID, sizeof(canid_t), &rx_id);
+ if (err < 0)
+ goto cancel_nlmsg_err;
+ }
+ break;
+ case CAN_J1939:
+ {
+ __u64 j1939_name;
+ __u32 j1939_pgn;
+ __u8 j1939_addr;
+
+ j1939_name = can_addr.can_addr.j1939.name;
+ j1939_pgn = can_addr.can_addr.j1939.pgn;
+ j1939_addr = can_addr.can_addr.j1939.addr;
+
+ err = nla_put(skb, CAN_DIAG_J1939_NAME, sizeof(j1939_name), &j1939_name);
+ if (err < 0)
+ goto cancel_nlmsg_err;
+
+ err = nla_put(skb, CAN_DIAG_J1939_PGN, sizeof(j1939_pgn), &j1939_pgn);
+ if (err < 0)
+ goto cancel_nlmsg_err;
+
+ err = nla_put(skb, CAN_DIAG_J1939_ADDR, sizeof(j1939_addr), &j1939_addr);
+ if (err < 0)
+ goto cancel_nlmsg_err;
+ }
+ break;
+ default:
+ break;
+ }
+
+exit_no_err:
+ nlmsg_end(skb, nlh);
+ return 0;
+
+cancel_nlmsg_err:
+ nlmsg_cancel(skb, nlh);
+ return err;
+}
+
+static int can_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
+{
+ int num = 0, s_num = cb->args[0];
+ struct can_diag_req *req;
+ struct net *net;
+ struct sock *sk;
+
+ net = sock_net(skb->sk);
+ req = nlmsg_data(cb->nlh);
+
+ lock_can_diag_mutex(net);
+ sk_for_each(sk, &net->can.sklist) {
+ if (num < s_num)
+ goto next;
+
+ if (sk_diag_fill(sk, skb, req,
+ sk_user_ns(NETLINK_CB(cb->skb).sk),
+ NETLINK_CB(cb->skb).portid,
+ cb->nlh->nlmsg_seq, NLM_F_MULTI,
+ sock_i_ino(sk)) < 0)
+ goto done;
+next:
+ num++;
+ }
+done:
+ unlock_can_diag_mutex(net);
+ cb->args[0] = num;
+
+ return skb->len;
+}
+
+static int can_diag_handler_dump(struct sk_buff *skb, struct nlmsghdr *h)
+{
+ int hdrlen = sizeof(struct can_diag_req);
+ struct net *net = sock_net(skb->sk);
+ struct can_diag_req *req;
+
+ if (nlmsg_len(h) < hdrlen)
+ return -EINVAL;
+
+ req = nlmsg_data(h);
+ if (req->sdiag_protocol)
+ return -EINVAL;
+
+ if (h->nlmsg_flags & NLM_F_DUMP) {
+ struct netlink_dump_control c = {
+ .dump = can_diag_dump
+ };
+ return netlink_dump_start(net->diag_nlsk, skb, h, &c);
+ }
+
+ return -EOPNOTSUPP;
+}
+
+static const struct sock_diag_handler can_diag_handler = {
+ .owner = THIS_MODULE,
+ .family = AF_CAN,
+ .dump = can_diag_handler_dump,
+};
+
+static int __init can_diag_init(void)
+{
+ pr_info("can: diagnostic module\n");
+ return sock_diag_register(&can_diag_handler);
+}
+
+static void __exit can_diag_exit(void)
+{
+ sock_diag_unregister(&can_diag_handler);
+}
+
+module_init(can_diag_init);
+module_exit(can_diag_exit);
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("CAN socket monitoring via SOCK_DIAG");
+MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_NETLINK, NETLINK_SOCK_DIAG, AF_CAN);
--
2.55.0
^ permalink raw reply related [flat|nested] 5+ messages in thread