[RFC PATCH 1/7] fou: Get net from sock_net if dev_net unavailable

[Tom Herbert]

With the implementation of Transports over UDP fou and gue build header
may be called before skb->dev is set. This patch checks skb->dev and
if it is not set then tries to get net from sock_net.

Signed-off-by: Tom Herbert <t...@herbertland.com>
---
 net/ipv4/fou.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/fou.c b/net/ipv4/fou.c
index 5f9207c..96260c6 100644
--- a/net/ipv4/fou.c
+++ b/net/ipv4/fou.c
@@ -807,13 +807,20 @@ int __fou_build_header(struct sk_buff *skb, struct 
ip_tunnel_encap *e,
                       u8 *protocol, __be16 *sport, int type)
 {
        int err;
+       struct net *net;
 
        err = iptunnel_handle_offloads(skb, type);
        if (err)
                return err;
 
-       *sport = e->sport ? : udp_flow_src_port(dev_net(skb->dev),
-                                               skb, 0, 0, false);
+       if (skb->dev)
+               net = dev_net(skb->dev);
+       else if (skb->sk)
+               net = sock_net(skb->sk);
+       else
+               return -EINVAL;
+
+       *sport = e->sport ? : udp_flow_src_port(net, skb, 0, 0, false);
 
        return 0;
 }
@@ -845,6 +852,14 @@ int __gue_build_header(struct sk_buff *skb, struct 
ip_tunnel_encap *e,
        void *data;
        bool need_priv = false;
        int err;
+       struct net *net;
+
+       if (skb->dev)
+               net = dev_net(skb->dev);
+       else if (skb->sk)
+               net = sock_net(skb->sk);
+       else
+               return -EINVAL;
 
        if ((e->flags & TUNNEL_ENCAP_FLAG_REMCSUM) &&
            skb->ip_summed == CHECKSUM_PARTIAL) {
@@ -860,8 +875,7 @@ int __gue_build_header(struct sk_buff *skb, struct 
ip_tunnel_encap *e,
                return err;
 
        /* Get source port (based on flow hash) before skb_push */
-       *sport = e->sport ? : udp_flow_src_port(dev_net(skb->dev),
-                                               skb, 0, 0, false);
+       *sport = e->sport ? : udp_flow_src_port(net, skb, 0, 0, false);
 
        hdrlen = sizeof(struct guehdr) + optlen;
 
-- 
2.8.0.rc2