From: Nicolas Dichtel nicolas.dichtel@6wind.com
[ Upstream commit f042365dbffea98fb8148c98c700402e8d099f02 ]
With an ebpf program that redirects packets through a xfrm interface, packets are dropped because no dst is attached to skb.
This could also be reproduced with an AF_PACKET socket, with the following python script (xfrm1 is a xfrm 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, ('xfrm1', 0x800, 0, 0))
It was also not possible to send an ip packet through an AF_PACKET socket because a LL header was expected. Let's remove those LL header constraints.
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/xfrm/xfrm_interface.c | 32 +++++++++++++++++++++++++------- 1 file changed, 25 insertions(+), 7 deletions(-)
diff --git a/net/xfrm/xfrm_interface.c b/net/xfrm/xfrm_interface.c index 0f5131bc3342d..a3db19d93fc5b 100644 --- a/net/xfrm/xfrm_interface.c +++ b/net/xfrm/xfrm_interface.c @@ -268,9 +268,6 @@ xfrmi_xmit2(struct sk_buff *skb, struct net_device *dev, struct flowi *fl) int err = -1; int mtu;
- if (!dst) - goto tx_err_link_failure; - dst_hold(dst); dst = xfrm_lookup_with_ifid(xi->net, dst, fl, NULL, 0, xi->p.if_id); if (IS_ERR(dst)) { @@ -343,6 +340,7 @@ static netdev_tx_t xfrmi_xmit(struct sk_buff *skb, struct net_device *dev) { struct xfrm_if *xi = netdev_priv(dev); struct net_device_stats *stats = &xi->dev->stats; + struct dst_entry *dst = skb_dst(skb); struct flowi fl; int ret;
@@ -352,10 +350,33 @@ static netdev_tx_t xfrmi_xmit(struct sk_buff *skb, struct net_device *dev) case htons(ETH_P_IPV6): xfrm_decode_session(skb, &fl, AF_INET6); memset(IP6CB(skb), 0, sizeof(*IP6CB(skb))); + 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); + stats->tx_carrier_errors++; + goto tx_err; + } + skb_dst_set(skb, dst); + } break; case htons(ETH_P_IP): xfrm_decode_session(skb, &fl, AF_INET); memset(IPCB(skb), 0, sizeof(*IPCB(skb))); + if (!dst) { + 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)) { + stats->tx_carrier_errors++; + goto tx_err; + } + skb_dst_set(skb, &rt->dst); + } break; default: goto tx_err; @@ -563,12 +584,9 @@ static void xfrmi_dev_setup(struct net_device *dev) { dev->netdev_ops = &xfrmi_netdev_ops; dev->type = ARPHRD_NONE; - dev->hard_header_len = ETH_HLEN; - dev->min_header_len = ETH_HLEN; dev->mtu = ETH_DATA_LEN; dev->min_mtu = ETH_MIN_MTU; - dev->max_mtu = ETH_DATA_LEN; - dev->addr_len = ETH_ALEN; + dev->max_mtu = IP_MAX_MTU; dev->flags = IFF_NOARP; dev->needs_free_netdev = true; dev->priv_destructor = xfrmi_dev_free;