[PATCH net-next] ip_gre: check packet length and mtu correctly in erspan_fb_xmit

[William Tu]

Similarly to early patch for erspan_xmit(), the ARPHDR_ETHER device
is the length of the whole ether packet.  So skb->len should subtract
the dev->hard_header_len.

Fixes: 1a66a836da63 ("gre: add collect_md mode to ERSPAN tunnel")
Signed-off-by: William Tu <u9012...@gmail.com>
Cc: Xin Long <lucien....@gmail.com>
---
 net/ipv4/ip_gre.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index b279c325c7f6..10b21fe5b3a6 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -579,7 +579,7 @@ static void erspan_fb_xmit(struct sk_buff *skb, struct 
net_device *dev,
        if (gre_handle_offloads(skb, false))
                goto err_free_rt;
 
-       if (skb->len > dev->mtu) {
+       if (skb->len - dev->hard_header_len > dev->mtu) {
                pskb_trim(skb, dev->mtu);
                truncate = true;
        }
-- 
2.7.4