net: dropreason: add SKB_DROP_REASON_RECURSION_LIMIT

[ Upstream commit d15d3de ]

ip[6]tunnel_xmit() can drop packets if a too deep recursion level
is detected.

Add SKB_DROP_REASON_RECURSION_LIMIT drop reason.

We will use this reason later in __dev_queue_xmit().

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Joe Damato <joe@dama.to>
Link: https://patch.msgid.link/20260312201824.203093-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 7fb4c19 ("net: pull headers in qdisc_pkt_len_segs_init()")
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: edumazet

include/net/dropreason-core.h

@@ -130,6 +130,7 @@
 	FN(DUALPI2_STEP_DROP)		\
 	FN(PSP_INPUT)			\
 	FN(PSP_OUTPUT)			\
+	FN(RECURSION_LIMIT)		\
 	FNe(MAX)
 
 /**
@@ -622,6 +623,8 @@ 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,
 	/**
 	 * @SKB_DROP_REASON_MAX: the maximum of core drop reasons, which
 	 * shouldn't be used as a real 'reason' - only for tracing code gen

include/net/ip6_tunnel.h

@@ -162,7 +162,7 @@ static inline void ip6tunnel_xmit(struct sock *sk, struct sk_buff *skb,
 					     dev->name);
 			DEV_STATS_INC(dev, tx_errors);
 		}
-		kfree_skb(skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_RECURSION_LIMIT);
 		return;
 	}
 

net/ipv4/ip_tunnel_core.c

@@ -65,7 +65,7 @@ void iptunnel_xmit(struct sock *sk, struct rtable *rt, struct sk_buff *skb,
 			DEV_STATS_INC(dev, tx_errors);
 		}
 		ip_rt_put(rt);
-		kfree_skb(skb);
+		kfree_skb_reason(skb, SKB_DROP_REASON_RECURSION_LIMIT);
 		return;
 	}