From 99c8719b79814cab3fd43519591dcc41c978a48c Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 25 Jun 2021 15:33:01 +0200 Subject: [PATCH 1/6] bareudp: allow redirecting bareudp packets to eth devices Even though bareudp transports L3 data (typically IP or MPLS), it needs to reset the mac_header pointer, so that other parts of the stack don't mistakenly access the outer header after the packet has been decapsulated. This allows to push an Ethernet header to bareudp packets and redirect them to an Ethernet device: $ tc filter add dev bareudp0 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 Without this patch, push_eth refuses to add an ethernet header because the skb appears to already have a MAC header. Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller --- drivers/net/bareudp.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/net/bareudp.c b/drivers/net/bareudp.c index edfad93e7b686..a7ee0af1af904 100644 --- a/drivers/net/bareudp.c +++ b/drivers/net/bareudp.c @@ -133,6 +133,7 @@ static int bareudp_udp_encap_recv(struct sock *sk, struct sk_buff *skb) skb->dev = bareudp->dev; oiph = skb_network_header(skb); skb_reset_network_header(skb); + skb_reset_mac_header(skb); if (!IS_ENABLED(CONFIG_IPV6) || family == AF_INET) err = IP_ECN_decapsulate(oiph, skb); From 7ad136fd288c0e0177eb29e04ec289e1b873b270 Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 25 Jun 2021 15:33:04 +0200 Subject: [PATCH 2/6] ipip: allow redirecting ipip and mplsip packets to eth devices Even though ipip transports IPv4 or MPLS packets, it needs to reset the mac_header pointer, so that other parts of the stack don't mistakenly access the outer header after the packet has been decapsulated. This allows to push an Ethernet header to ipip or mplsip packets and redirect them to an Ethernet device: $ tc filter add dev ipip0 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 Without this patch, push_eth refuses to add an ethernet header because the skb appears to already have a MAC header. Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller --- net/ipv4/ipip.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/net/ipv4/ipip.c b/net/ipv4/ipip.c index d5bfa087c23ad..266c65577ba68 100644 --- a/net/ipv4/ipip.c +++ b/net/ipv4/ipip.c @@ -242,6 +242,8 @@ static int ipip_tunnel_rcv(struct sk_buff *skb, u8 ipproto) if (!tun_dst) return 0; } + skb_reset_mac_header(skb); + return ip_tunnel_rcv(tunnel, skb, tpi, tun_dst, log_ecn_error); } From 730eed2772e740c30229d03e3d578cc00a5ae304 Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 25 Jun 2021 15:33:08 +0200 Subject: [PATCH 3/6] sit: allow redirecting ip6ip, ipip and mplsip packets to eth devices Even though sit transports L3 data (IPv6, IPv4 or MPLS) packets, it needs to reset the mac_header pointer, so that other parts of the stack don't mistakenly access the outer header after the packet has been decapsulated. There are two rx handlers to modify: ipip6_rcv() for the ip6ip mode and sit_tunnel_rcv() which is used to re-implement the ipip and mplsip modes of ipip.ko. This allows to push an Ethernet header to sit packets and redirect them to an Ethernet device: $ tc filter add dev sit0 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 Without this patch, push_eth refuses to add an ethernet header because the skb appears to already have a MAC header. Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller --- net/ipv6/sit.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c index e0a39b0bb4c10..df5bea8184101 100644 --- a/net/ipv6/sit.c +++ b/net/ipv6/sit.c @@ -710,6 +710,8 @@ static int ipip6_rcv(struct sk_buff *skb) * old iph is no longer valid */ iph = (const struct iphdr *)skb_mac_header(skb); + skb_reset_mac_header(skb); + err = IP_ECN_decapsulate(iph, skb); if (unlikely(err)) { if (log_ecn_error) @@ -780,6 +782,8 @@ static int sit_tunnel_rcv(struct sk_buff *skb, u8 ipproto) tpi = &ipip_tpi; if (iptunnel_pull_header(skb, 0, tpi->proto, false)) goto drop; + skb_reset_mac_header(skb); + return ip_tunnel_rcv(tunnel, skb, tpi, NULL, log_ecn_error); } From aab1e898c26c3e4289c62b6d6482948672fab939 Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 25 Jun 2021 15:33:13 +0200 Subject: [PATCH 4/6] 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(-) diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c index a68bf4c6fe9b7..12dca0c85f3c3 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); From da5a2e49f064a86a3b102b20c545f855a7298394 Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 25 Jun 2021 15:33:17 +0200 Subject: [PATCH 5/6] ip6_tunnel: allow redirecting ip6gre and ipxip6 packets to eth devices Reset the mac_header pointer even when the tunnel transports only L3 data (in the ARPHRD_ETHER case, this is already done by eth_type_trans). This prevents other parts of the stack from mistakenly accessing the outer header after the packet has been decapsulated. In practice, this allows to push an Ethernet header to ipip6, ip6ip6, mplsip6 or ip6gre packets and redirect them to an Ethernet device: $ tc filter add dev ip6tnl0 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 Without this patch, push_eth refuses to add an ethernet header because the skb appears to already have a MAC header. Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller --- net/ipv6/ip6_tunnel.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c index 288bafded9989..0b8a38687ce47 100644 --- a/net/ipv6/ip6_tunnel.c +++ b/net/ipv6/ip6_tunnel.c @@ -837,6 +837,7 @@ static int __ip6_tnl_rcv(struct ip6_tnl *tunnel, struct sk_buff *skb, skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN); } else { skb->dev = tunnel->dev; + skb_reset_mac_header(skb); } skb_reset_network_header(skb); From b2d898c8a523f44ee7b3eea608e81a6e2264579f Mon Sep 17 00:00:00 2001 From: Guillaume Nault Date: Fri, 25 Jun 2021 15:33:23 +0200 Subject: [PATCH 6/6] gtp: reset mac_header after decap For consistency with other L3 tunnel devices, reset the mac_header pointer after decapsulation. This makes the mac_header 0 bytes long, thus making it clear that this skb has no mac_header. Compile tested only. Signed-off-by: Guillaume Nault Signed-off-by: David S. Miller --- drivers/net/gtp.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index 1c9023d47e008..30e0a10595a16 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c @@ -201,6 +201,7 @@ static int gtp_rx(struct pdp_ctx *pctx, struct sk_buff *skb, * calculate the transport header. */ skb_reset_network_header(skb); + skb_reset_mac_header(skb); skb->dev = pctx->dev;