Commit 2798e36d authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

tcp: add TCP_MINTTL drop reason 



In the unlikely case incoming packets are dropped because
of IP_MINTTL / IPV6_MINHOPCOUNT constraints...

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20230201174345.2708943-1-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 0719bc3a

include/net/dropreason.h

+6 −0
Original line number Diff line number Diff line
@@ -71,6 +71,7 @@ 
	FN(DUP_FRAG)			\

	FN(FRAG_REASM_TIMEOUT)		\

	FN(FRAG_TOO_FAR)		\

	FN(TCP_MINTTL)			\

	FNe(MAX)



/**
@@ -312,6 +313,11 @@ enum skb_drop_reason { 
	 * (/proc/sys/net/ipv4/ipfrag_max_dist)

	 */

	SKB_DROP_REASON_FRAG_TOO_FAR,

	/**

	 * @SKB_DROP_REASON_TCP_MINTTL: ipv4 ttl or ipv6 hoplimit below

	 * the threshold (IP_MINTTL or IPV6_MINHOPCOUNT).

	 */

	SKB_DROP_REASON_TCP_MINTTL,

	/**

	 * @SKB_DROP_REASON_MAX: the maximum of drop reason, which shouldn't be

	 * used as a real 'reason'

net/ipv4/tcp_ipv4.c

+1 −0
Original line number Diff line number Diff line
@@ -2102,6 +2102,7 @@ int tcp_v4_rcv(struct sk_buff *skb) 
		/* min_ttl can be changed concurrently from do_ip_setsockopt() */

		if (unlikely(iph->ttl < READ_ONCE(inet_sk(sk)->min_ttl))) {

			__NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);

			drop_reason = SKB_DROP_REASON_TCP_MINTTL;

			goto discard_and_relse;

		}

	}

net/ipv6/tcp_ipv6.c

+2 −1
Original line number Diff line number Diff line
@@ -1708,8 +1708,9 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb) 


	if (static_branch_unlikely(&ip6_min_hopcount)) {

		/* min_hopcount can be changed concurrently from do_ipv6_setsockopt() */

		if (hdr->hop_limit < READ_ONCE(tcp_inet6_sk(sk)->min_hopcount)) {

		if (unlikely(hdr->hop_limit < READ_ONCE(tcp_inet6_sk(sk)->min_hopcount))) {

			__NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);

			drop_reason = SKB_DROP_REASON_TCP_MINTTL;

			goto discard_and_relse;

		}

	}