[net,v3,1/4] ipv4: fix source address selection with route leak

Commit Message

Nicolas Dichtel July 8, 2024, 6:15 p.m. UTC

By default, an address assigned to the output interface is selected when
the source address is not specified. This is problematic when a route,
configured in a vrf, uses an interface from another vrf (aka route leak).
The original vrf does not own the selected source address.

Let's add a check against the output interface and call the appropriate
function to select the source address.

CC: [e-mail]
Fixes: 8cbb512c923d ("net: Add source address lookup op for VRF")
Signed-off-by: Nicolas Dichtel <[e-mail]>
---
 net/ipv4/fib_semantics.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

Comments

David Ahern July 9, 2024, 3:06 a.m. UTC | #1

On 7/8/24 12:15 PM, Nicolas Dichtel wrote:
> By default, an address assigned to the output interface is selected when
> the source address is not specified. This is problematic when a route,
> configured in a vrf, uses an interface from another vrf (aka route leak).
> The original vrf does not own the selected source address.
> 
> Let's add a check against the output interface and call the appropriate
> function to select the source address.
> 
> CC: [e-mail]
> Fixes: 8cbb512c923d ("net: Add source address lookup op for VRF")
> Signed-off-by: Nicolas Dichtel <[e-mail]>
> ---
>  net/ipv4/fib_semantics.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 

Reviewed-by: David Ahern <[e-mail]>

Patch

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index f669da98d11d..8956026bc0a2 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -2270,6 +2270,15 @@  void fib_select_path(struct net *net, struct fib_result *res,
 		fib_select_default(fl4, res);
 
 check_saddr:
-	if (!fl4->saddr)
-		fl4->saddr = fib_result_prefsrc(net, res);
+	if (!fl4->saddr) {
+		struct net_device *l3mdev;
+
+		l3mdev = dev_get_by_index_rcu(net, fl4->flowi4_l3mdev);
+
+		if (!l3mdev ||
+		    l3mdev_master_dev_rcu(FIB_RES_DEV(*res)) == l3mdev)
+			fl4->saddr = fib_result_prefsrc(net, res);
+		else
+			fl4->saddr = inet_select_addr(l3mdev, 0, RT_SCOPE_LINK);
+	}
 }