From aab1e898c26c3e4289c62b6d6482948672fab939 Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 25 Jun 2021 15:33:13 +0200 Subject: gre: let mac_header point to outer header only when necessary Commit e271c7b4420d ("gre: do not keep the GRE header around in collect medata mode") did reset the mac_header for the collect_md case. Let's extend this behaviour to classical gre devices as well. ipgre_header_parse() seems to be the only case that requires mac_header to point to the outer header. We can detect this case accurately by checking ->header_ops. For all other cases, we can reset mac_header. This allows to push an Ethernet header to ipgre packets and redirect them to an Ethernet device: $ tc filter add dev gre0 ingress matchall \ action vlan push_eth dst_mac 00:00:5e:00:53:01 \ src_mac 00:00:5e:00:53:00 \ action mirred egress redirect dev eth0 Before this patch, this worked only for collect_md gre devices. Now this works for regular gre devices as well. Only the special case of gre devices that use ipgre_header_ops isn't supported. Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller --- net/ipv4/ip_gre.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'net/ipv4/ip_gre.c') diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index a68bf4c6fe9b..12dca0c85f3c 100644 --- a/net/ipv4/ip_gre.c +++ b/net/ipv4/ip_gre.c @@ -107,6 +107,8 @@ module_param(log_ecn_error, bool, 0644); MODULE_PARM_DESC(log_ecn_error, "Log packets received with corrupted ECN"); static struct rtnl_link_ops ipgre_link_ops __read_mostly; +static const struct header_ops ipgre_header_ops; + static int ipgre_tunnel_init(struct net_device *dev); static void erspan_build_header(struct sk_buff *skb, u32 id, u32 index, @@ -364,7 +366,10 @@ static int __ipgre_rcv(struct sk_buff *skb, const struct tnl_ptk_info *tpi, raw_proto, false) < 0) goto drop; - if (tunnel->dev->type != ARPHRD_NONE) + /* Special case for ipgre_header_parse(), which expects the + * mac_header to point to the outer IP header. + */ + if (tunnel->dev->header_ops == &ipgre_header_ops) skb_pop_mac_header(skb); else skb_reset_mac_header(skb); -- cgit v1.2.3