[PATCH net-next v4 4/7] ipv6: Set HBH and DestOpt limits to 2
From: Tom Herbert <hidden>
Date: 2026-01-21 21:49:57
Subsystem:
networking [general], networking [ipv4/ipv6], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, David Ahern, Ido Schimmel, Linus Torvalds
Set the default limits of non-padding Hop-by-Hop and Destination options to 2. This means that if a packet contains more then two non-padding options then it will be dropped. The previous limit was 8, but that was too liberal considering that the stack only support two Destination Options and the most Hop-by-Hop options likely to ever be in the same packet are IOAM and JUMBO. The limit can be increased via sysctl for private use and experimenation. Signed-off-by: Tom Herbert <redacted> --- include/net/ipv6.h | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index c7f597da01cd..31d270c8c2e4 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h@@ -86,9 +86,12 @@ struct ip_tunnel_info; * silently discarded. */ -/* Default limits for Hop-by-Hop and Destination options */ -#define IP6_DEFAULT_MAX_DST_OPTS_CNT 8 -#define IP6_DEFAULT_MAX_HBH_OPTS_CNT 8 +/* Default limits for Hop-by-Hop and Destination non-padding options. The + * default value for both is 2. This sets a limit at two non-padding options + * (see sysctl documention) + */ +#define IP6_DEFAULT_MAX_DST_OPTS_CNT 2 +#define IP6_DEFAULT_MAX_HBH_OPTS_CNT 2 #define IP6_DEFAULT_MAX_DST_OPTS_LEN INT_MAX /* No limit */ #define IP6_DEFAULT_MAX_HBH_OPTS_LEN INT_MAX /* No limit */
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2.43.0