[PATCH iproute2-next] bridge: fdb: Use 'struct ndmsg' for FDB dumping

[PATCH iproute2-next] bridge: fdb: Use 'struct ndmsg' for FDB dumping

[Ido Schimmel]

Since commit aea41afcfd6d ("ip bridge: Set NETLINK_GET_STRICT_CHK on
socket") iproute2 uses strict checking on kernels that support it. This
causes FDB dumping to fail [1], as iproute2 uses 'struct ifinfomsg'
whereas the kernel expects 'struct ndmsg'.

Note that with this change iproute2 continues to work on old kernels
that do not support strict checking, but contain the fix introduced in
kernel commit bd961c9bc664 ("rtnetlink: fix rtnl_fdb_dump() for ndmsg
header").

[1]
# bridge fdb show
[ 5365.137224] netlink: 4 bytes leftover after parsing attributes in process `bridge'.
Error: bytes leftover after parsing attributes.
Dump terminated

Fixes: aea41afcfd6d ("ip bridge: Set NETLINK_GET_STRICT_CHK on socket")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
---
 bridge/fdb.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/bridge/fdb.c b/bridge/fdb.c
index a5abc1b6c78d..a7a0d8052307 100644
--- a/bridge/fdb.c
+++ b/bridge/fdb.c
@@ -260,16 +260,16 @@ static int fdb_show(int argc, char **argv)
 {
 	struct {
 		struct nlmsghdr	n;
-		struct ifinfomsg	ifm;
+		struct ndmsg		ndm;
 		char			buf[256];
 	} req = {
-		.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
-		.ifm.ifi_family = PF_BRIDGE,
+		.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct ndmsg)),
+		.ndm.ndm_family = PF_BRIDGE,
 	};
 
 	char *filter_dev = NULL;
 	char *br = NULL;
-	int msg_size = sizeof(struct ifinfomsg);
+	int msg_size = sizeof(struct ndmsg);
 
 	while (argc > 0) {
 		if ((strcmp(*argv, "brport") == 0) || strcmp(*argv, "dev") == 0) {
@@ -313,10 +313,10 @@ static int fdb_show(int argc, char **argv)
 		filter_index = ll_name_to_index(filter_dev);
 		if (!filter_index)
 			return nodev(filter_dev);
-		req.ifm.ifi_index = filter_index;
+		req.ndm.ndm_ifindex = filter_index;
 	}
 
-	if (rtnl_dump_request(&rth, RTM_GETNEIGH, &req.ifm, msg_size) < 0) {
+	if (rtnl_dump_request(&rth, RTM_GETNEIGH, &req.ndm, msg_size) < 0) {
 		perror("Cannot send dump request");
 		exit(1);
 	}
-- 
2.20.1

Re: [PATCH iproute2-next] bridge: fdb: Use 'struct ndmsg' for FDB dumping

[David Ahern]

On 12/30/18 10:14 AM, Ido Schimmel wrote:
> Since commit aea41afcfd6d ("ip bridge: Set NETLINK_GET_STRICT_CHK on
> socket") iproute2 uses strict checking on kernels that support it. This
> causes FDB dumping to fail [1], as iproute2 uses 'struct ifinfomsg'
> whereas the kernel expects 'struct ndmsg'.
> 
> Note that with this change iproute2 continues to work on old kernels
> that do not support strict checking, but contain the fix introduced in
> kernel commit bd961c9bc664 ("rtnetlink: fix rtnl_fdb_dump() for ndmsg
> header").
> 
> [1]
> # bridge fdb show
> [ 5365.137224] netlink: 4 bytes leftover after parsing attributes in process `bridge'.
> Error: bytes leftover after parsing attributes.
> Dump terminated
> 
> Fixes: aea41afcfd6d ("ip bridge: Set NETLINK_GET_STRICT_CHK on socket")
> Signed-off-by: Ido Schimmel <idosch@mellanox.com>
> ---
>  bridge/fdb.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)

applied to iproute2-next. Thanks, Ido.

Re: [PATCH iproute2-next] bridge: fdb: Use 'struct ndmsg' for FDB dumping

[Stephen Hemminger]

On Sun, 30 Dec 2018 18:03:47 -0700
David Ahern <dsahern@gmail.com> wrote:

> On 12/30/18 10:14 AM, Ido Schimmel wrote:
> > Since commit aea41afcfd6d ("ip bridge: Set NETLINK_GET_STRICT_CHK on
> > socket") iproute2 uses strict checking on kernels that support it. This
> > causes FDB dumping to fail [1], as iproute2 uses 'struct ifinfomsg'
> > whereas the kernel expects 'struct ndmsg'.
> > 
> > Note that with this change iproute2 continues to work on old kernels
> > that do not support strict checking, but contain the fix introduced in
> > kernel commit bd961c9bc664 ("rtnetlink: fix rtnl_fdb_dump() for ndmsg
> > header").

Sorry, I don't think that is good enough backward compatibility guarantee.
Iproute2 should work on really old kernels like 2.6.32. If not then then iproute2
utility is broken or the changes to the kernel API were incorrect.

You can't depend on some old commit.

Re: [PATCH iproute2-next] bridge: fdb: Use 'struct ndmsg' for FDB dumping

[Ido Schimmel]

On Mon, Dec 31, 2018 at 08:25:38PM -0800, Stephen Hemminger wrote:
> On Sun, 30 Dec 2018 18:03:47 -0700
> David Ahern <dsahern@gmail.com> wrote:
> 
> > On 12/30/18 10:14 AM, Ido Schimmel wrote:
> > > Since commit aea41afcfd6d ("ip bridge: Set NETLINK_GET_STRICT_CHK on
> > > socket") iproute2 uses strict checking on kernels that support it. This
> > > causes FDB dumping to fail [1], as iproute2 uses 'struct ifinfomsg'
> > > whereas the kernel expects 'struct ndmsg'.
> > > 
> > > Note that with this change iproute2 continues to work on old kernels
> > > that do not support strict checking, but contain the fix introduced in
> > > kernel commit bd961c9bc664 ("rtnetlink: fix rtnl_fdb_dump() for ndmsg
> > > header").
> 
> Sorry, I don't think that is good enough backward compatibility guarantee.
> Iproute2 should work on really old kernels like 2.6.32. If not then then iproute2
> utility is broken or the changes to the kernel API were incorrect.

I found two more issues for which I have patches. I tested with and
without strict checking and I'll test on some old kernels as well. No
intention to break backward compatibility. Will Cc you.

Thanks