ip_gre: check packet length and mtu correctly in erspan_xmit

lxin · davem330 · commit 5513d08d2951 · 2017-10-01T22:30:32.000-07:00
As a ARPHRD_ETHER device, skb->len in erspan_xmit is the length of the whole ether packet. So before checking if a packet size exceeds the mtu, skb->len should subtract dev->hard_header_len. Otherwise, all packets with max size according to mtu would be trimmed to be truncated packet. Fixes: 84e54fe ("gre: introduce native tunnel support for ERSPAN") Signed-off-by: Xin Long <lucien.xin@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
@@ -731,7 +731,7 @@ static netdev_tx_t erspan_xmit(struct sk_buff *skb,
 	if (skb_cow_head(skb, dev->needed_headroom))
 		goto free_skb;
 
-	if (skb->len > dev->mtu) {
+	if (skb->len - dev->hard_header_len > dev->mtu) {
 		pskb_trim(skb, dev->mtu);
 		truncate = true;
 	}

Original file line number	Diff line number	Diff line change
`@@ -731,7 +731,7 @@ static netdev_tx_t erspan_xmit(struct sk_buff *skb,`
`731`	`731`	`if (skb_cow_head(skb, dev->needed_headroom))`
`732`	`732`	`goto free_skb;`
`733`	`733`
`734`		`- if (skb->len > dev->mtu) {`
	`734`	`+ if (skb->len - dev->hard_header_len > dev->mtu) {`
`735`	`735`	`pskb_trim(skb, dev->mtu);`
`736`	`736`	`truncate = true;`
`737`	`737`	`}`