[PATCH net-next 4/4] vxlan: report a circular route as SKB_DROP_REASON_RECURSION_LIMIT
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WARM3d
IN NET-NEXT
From: Anton Danilov <hidden>
Date: 2026-10-05 20:14:30
Also in:
lkml
Subsystem:
networking drivers, networking [general], the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
Queued in net-next as d476bb7c0efd on 2026-10-08.
udp_tunnel_dst_lookup() and udp_tunnel6_dst_lookup() return -ELOOP when the route to the remote end goes out of the vxlan device itself, and vxlan_xmit_one() counts that in collisions, apart from the -ENETUNREACH of a failed lookup. The drop reason does not tell them apart: both are reported as SKB_DROP_REASON_IP_OUTNOROUTES, which describes a failed route lookup. Such a route would send the encapsulated packet back into the device it leaves, which is the dead loop on a virtual device that SKB_DROP_REASON_RECURSION_LIMIT describes. Report the -ELOOP case with that reason, and add the tunnel case to the description of the reason as an example. ip_tunnel and ip6_tunnel make the same check, rt->dst.dev == dev in ip_tunnel_xmit() and ip_md_tunnel_xmit() and tdev == dev in ip6_tnl_xmit(), and can report it with the same reason. Assisted-by: LLM Signed-off-by: Anton Danilov <redacted> --- drivers/net/vxlan/vxlan_core.c | 10 ++++++++-- include/net/dropreason-core.h | 6 +++++- 2 files changed, 13 insertions(+), 3 deletions(-)
diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
index 0d98e29e2d72..7c94a630d184 100644
--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c@@ -2547,7 +2547,10 @@ void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev, tos, use_cache ? dst_cache : NULL); if (IS_ERR(rt)) { err = PTR_ERR(rt); - reason = SKB_DROP_REASON_IP_OUTNOROUTES; + if (err == -ELOOP) + reason = SKB_DROP_REASON_RECURSION_LIMIT; + else + reason = SKB_DROP_REASON_IP_OUTNOROUTES; goto tx_error; }
@@ -2633,7 +2636,10 @@ void vxlan_xmit_one(struct sk_buff *skb, struct net_device *dev, if (IS_ERR(ndst)) { err = PTR_ERR(ndst); ndst = NULL; - reason = SKB_DROP_REASON_IP_OUTNOROUTES; + if (err == -ELOOP) + reason = SKB_DROP_REASON_RECURSION_LIMIT; + else + reason = SKB_DROP_REASON_IP_OUTNOROUTES; goto tx_error; }
diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 40a27d8887af..664249924219 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h@@ -613,7 +613,11 @@ enum skb_drop_reason { SKB_DROP_REASON_PSP_INPUT, /** @SKB_DROP_REASON_PSP_OUTPUT: PSP output checks failed */ SKB_DROP_REASON_PSP_OUTPUT, - /** @SKB_DROP_REASON_RECURSION_LIMIT: Dead loop on virtual device. */ + /** + * @SKB_DROP_REASON_RECURSION_LIMIT: Dead loop on virtual device, e.g. a + * tunnel whose route to its remote end goes out of the tunnel device + * itself. + */ SKB_DROP_REASON_RECURSION_LIMIT, /** * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which
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