From 505b6d296c486ef7d1274f279d4c43a172f63224 Mon Sep 17 00:00:00 2001 From: Zhiling Zou Date: Thu, 13 Aug 2026 00:22:34 +0800 Subject: [PATCH] ip6_gre: fix hardware header length for NBMA tunnels ip6gre_tnl_link_config_route() accumulates the lower device's hardware header length into dev->hard_header_len whenever header_ops is set. This is incorrect for both users of header_ops. ip6gretap and ip6erspan have a fixed Ethernet hardware header length. For an NBMA ip6gre tunnel, ip6gre_header() creates only the GRE header, the optional FOU or GUE header, and the outer IPv6 header. The lower device header is headroom needed later, not part of the tunnel device's hardware header. Keep the lower device header in needed_headroom. Set hard_header_len to the tunnel header length only for ARPHRD_IP6GRE devices with header_ops, and leave the fixed Ethernet header length unchanged for tap and erspan devices. Fixes: 832ba596494b ("net: ip6_gre: set dev->hard_header_len when using header_ops") Cc: stable@vger.kernel.org Suggested-by: Ido Schimmel Signed-off-by: Zhiling Zou Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/64b46542bbe1701f07702aaa50273e2a87903db5.1786542637.git.zhilinz@nebusec.ai Signed-off-by: Paolo Abeni --- net/ipv6/ip6_gre.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-) diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index b843116e9b70..70c171091020 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -1137,13 +1137,8 @@ static void ip6gre_tnl_link_config_route(struct ip6_tnl *t, int set_mtu, return; if (rt->dst.dev) { - unsigned short dst_len = rt->dst.dev->hard_header_len + - t_hlen; - - if (t->dev->header_ops) - dev->hard_header_len = dst_len; - else - dev->needed_headroom = dst_len; + dev->needed_headroom = rt->dst.dev->hard_header_len + + t_hlen; if (set_mtu) { int mtu = rt->dst.dev->mtu - t_hlen; @@ -1171,8 +1166,8 @@ static int ip6gre_calc_hlen(struct ip6_tnl *tunnel) t_hlen = tunnel->hlen + sizeof(struct ipv6hdr); - if (tunnel->dev->header_ops) - tunnel->dev->hard_header_len = LL_MAX_HEADER + t_hlen; + if (tunnel->dev->header_ops && tunnel->dev->type == ARPHRD_IP6GRE) + tunnel->dev->hard_header_len = t_hlen; else tunnel->dev->needed_headroom = LL_MAX_HEADER + t_hlen;