sit: update dev->needed_headroom in ipip6_tunnel_bind_dev()

When a tunnel device is bound with the underlying device, its
dev->needed_headroom needs to be updated properly. IPv4 tunnels
already do the same in ip_tunnel_bind_dev(). Otherwise we may
not have enough header room for skb, especially after commit
b17f709a2401 ("gue: TX support for using remote checksum offload option").

Fixes: 32b8a8e59c9c ("sit: add IPv4 over IPv4 support")
Reported-by: Palash Oswal <oswalpalash@gmail.com>
Link: https://lore.kernel.org/netdev/CAGyP=7fDcSPKu6nttbGwt7RXzE3uyYxLjCSE97J64pRxJP8jPA@mail.gmail.com/
Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 063560e2cb1a8692f52b7d88573994805ac20c0e..cc24cefdb85c0944c03c019b1c4214302d18e2c8 100644 (file)
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c
@@ -1095,12 +1095,13 @@ tx_err:
 
 static void ipip6_tunnel_bind_dev(struct net_device *dev)
 {
+       struct ip_tunnel *tunnel = netdev_priv(dev);
+       int t_hlen = tunnel->hlen + sizeof(struct iphdr);
        struct net_device *tdev = NULL;
-       struct ip_tunnel *tunnel;
+       int hlen = LL_MAX_HEADER;
        const struct iphdr *iph;
        struct flowi4 fl4;
 
-       tunnel = netdev_priv(dev);
        iph = &tunnel->parms.iph;
 
        if (iph->daddr) {
@@ -1123,14 +1124,15 @@ static void ipip6_tunnel_bind_dev(struct net_device *dev)
                tdev = __dev_get_by_index(tunnel->net, tunnel->parms.link);
 
        if (tdev && !netif_is_l3_master(tdev)) {
-               int t_hlen = tunnel->hlen + sizeof(struct iphdr);
                int mtu;
 
                mtu = tdev->mtu - t_hlen;
                if (mtu < IPV6_MIN_MTU)
                        mtu = IPV6_MIN_MTU;
                WRITE_ONCE(dev->mtu, mtu);
+               hlen = tdev->hard_header_len + tdev->needed_headroom;
        }
+       dev->needed_headroom = t_hlen + hlen;
 }
 
 static void ipip6_tunnel_update(struct ip_tunnel *t, struct ip_tunnel_parm *p,