Re: POSSIBLE BUG: selftests/net/fcnal-test.sh: [FAIL] in vrf "bind - ns-B IPv6 LLA" test

On 5/31/23 20:11, Guillaume Nault wrote:

On Wed, May 24, 2023 at 02:17:09PM +0200, Mirsad Todorovac wrote:

quoted

Hi,

Hi Mirsad,

quoted

The very recent 6.4-rc3 kernel build with AlmaLinux 8.7 on LENOVO 10TX000VCR
desktop box fails one test:

[root@host net]# ./fcnal-test.sh
[...]
TEST: ping out, vrf device+address bind - ns-B loopback IPv6                  [ OK ]
TEST: ping out, vrf device+address bind - ns-B IPv6 LLA                       [FAIL]
TEST: ping in - ns-A IPv6                                                     [ OK ]
[...]
Tests passed: 887
Tests failed:   1
[root@host net]#

This test also fails on -net. The problem is specific to ping sockets
(same test passes with raw sockets). I believe this test has always
failed since fcnal-test.sh started using net.ipv4.ping_group_range
(commit e71b7f1f44d3 ("selftests: add ping test with ping_group_range
tuned")).

The executed command is:

ip netns exec ns-A ip vrf exec red /usr/bin/ping6 -c1 -w1 -I 2001:db8:3::1 fe80::a846:b5ff:fe4c:da4e%eth1

So ping6 is executed inside VRF 'red' and sets .sin6_scope_id to 'eth1'
(which is a slave device of VRF 'red'). Therefore, we have
sk->sk_bound_dev_if == 'red' and .sin6_scope_id == 'eth1'. This fails
because ping_v6_sendmsg() expects them to be equal:

static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
{
...
                 if (__ipv6_addr_needs_scope_id(ipv6_addr_type(daddr)))
                         oif = u->sin6_scope_id;
...
         if ((__ipv6_addr_needs_scope_id(addr_type) && !oif) ||
             (addr_type & IPV6_ADDR_MAPPED) ||
             (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if)) <-- oif='eth1', but ->sk_bound_dev_if='red'
                 return -EINVAL;
...
}

I believe this condition should be relaxed to allow the case where
->sk_bound_dev_if is oif's master device (and maybe there are other
VRF cases to also consider).

I've tried something like this, but something makes the kernel stuck
here:

TEST: ping out, blocked by route - ns-B loopback IPv6                         [ OK ]
TEST: ping out, device bind, blocked by route - ns-B loopback IPv6            [ OK ]
TEST: ping in, blocked by route - ns-A loopback IPv6                          [ OK ]
TEST: ping out, unreachable route - ns-B loopback IPv6                        [ OK ]
TEST: ping out, device bind, unreachable route - ns-B loopback IPv6           [ OK ]

#################################################################
With VRF

[hanged process and kernel won't shutdown]

The code is:

---
  net/ipv6/ping.c | 12 +++++++++++-
  1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/ping.c b/net/ipv6/ping.c
index c4835dbdfcff..81293e902293 100644
--- a/net/ipv6/ping.c
+++ b/net/ipv6/ping.c

@@ -73,6 +73,9 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
         struct rt6_info *rt;
         struct pingfakehdr pfh;
         struct ipcm6_cookie ipc6;
+       struct net *net = sock_net(sk);
+       struct net_device *dev = NULL;
+       struct net_device *mdev = NULL;
  
         err = ping_common_sendmsg(AF_INET6, msg, len, &user_icmph,
                                   sizeof(user_icmph));

@@ -111,10 +114,17 @@ static int ping_v6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
         else if (!oif)
                 oif = np->ucast_oif;
  
+       if (oif) {
+               dev = dev_get_by_index(net, oif);
+               mdev = netdev_master_upper_dev_get(dev);
+       }
+
         addr_type = ipv6_addr_type(daddr);
         if ((__ipv6_addr_needs_scope_id(addr_type) && !oif) ||
             (addr_type & IPV6_ADDR_MAPPED) ||
-           (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if))
+           (oif && sk->sk_bound_dev_if && oif != sk->sk_bound_dev_if &&
+                   !(mdev && sk->sk_bound_dev_if &&
+                             mdev != dev_get_by_index(net, sk->sk_bound_dev_if))))
                 return -EINVAL;
  
         ipcm6_init_sk(&ipc6, np);

I am obviously doing something very stupid.

Regards,
Mirsad