[PATCH 5.4 67/90] vti[6]: fix packet tx through bpf_redirect()

Greg Kroah-Hartman
2020-02-03T16:36:23Z

From: Nicolas Dichtel <nicolas.dichtel@6wind.com>

[ Upstream commit 95224166a9032ff5d08fca633d37113078ce7d01 ]

With an ebpf program that redirects packets through a vti[6] interface,
the packets are dropped because no dst is attached.

This could also be reproduced with an AF_PACKET socket, with the following
python script (vti1 is an ip_vti interface):

import socket
send_s = socket.socket(socket.AF_PACKET, socket.SOCK_RAW, 0)
# scapy
# p = IP(src='10.100.0.2', dst='10.200.0.1')/ICMP(type='echo-request')
# raw(p)
req = b'E\x00\x00\x1c\x00\x01\x00\x00@\x01e\xb2\nd\x00\x02\n\xc8\x00\x01\x08\x00\xf7\xff\x00\x00\x00\x00'
send_s.sendto(req, ('vti1', 0x800, 0, 0))

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/ipv4/ip_vti.c | 13 +++++++++++--
net/ipv6/ip6_vti.c | 13 +++++++++++--
2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/ip_vti.c b/net/ipv4/ip_vti.c
index fb9f6d60c27cd..79eef5db336a4 100644
--- a/net/ipv4/ip_vti.c
+++ b/net/ipv4/ip_vti.c
@@ -187,8 +187,17 @@ static netdev_tx_t vti_xmit(struct sk_buff *skb, struct net_device *dev,
int mtu;

if (!dst) {
- dev->stats.tx_carrier_errors++;
- goto tx_error_icmp;
+ struct rtable *rt;
+
+ fl->u.ip4.flowi4_oif = dev->ifindex;
+ fl->u.ip4.flowi4_flags |= FLOWI_FLAG_ANYSRC;
+ rt = __ip_route_output_key(dev_net(dev), &fl->u.ip4);
+ if (IS_ERR(rt)) {
+ dev->stats.tx_carrier_errors++;
+ goto tx_error_icmp;
+ }
+ dst = &rt->dst;
+ skb_dst_set(skb, dst);
}

dst_hold(dst);
diff --git a/net/ipv6/ip6_vti.c b/net/ipv6/ip6_vti.c
index 6f08b760c2a7c..524006aa0d78a 100644
--- a/net/ipv6/ip6_vti.c
+++ b/net/ipv6/ip6_vti.c
@@ -449,8 +449,17 @@ vti6_xmit(struct sk_buff *skb, struct net_device *dev, struct flowi *fl)
int err = -1;
int mtu;

- if (!dst)
- goto tx_err_link_failure;
+ if (!dst) {
+ fl->u.ip6.flowi6_oif = dev->ifindex;
+ fl->u.ip6.flowi6_flags |= FLOWI_FLAG_ANYSRC;
+ dst = ip6_route_output(dev_net(dev), NULL, &fl->u.ip6);
+ if (dst->error) {
+ dst_release(dst);
+ dst = NULL;
+ goto tx_err_link_failure;
+ }
+ skb_dst_set(skb, dst);
+ }

dst_hold(dst);
dst = xfrm_lookup(t->net, dst, fl, NULL, 0);
--
2.20.1