gso: Support partial splitting at the frag_list pointer

Since commit 8a29111c7 ("net: gro: allow to build full sized skb")
gro may build buffers with a frag_list. This can hurt forwarding
because most NICs can't offload such packets, they need to be
segmented in software. This patch splits buffers with a frag_list
at the frag_list pointer into buffers that can be TSO offloaded.

Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Acked-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 25 insertions, 14 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index e94b47be0019..1effc986739e 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1192,7 +1192,7 @@ EXPORT_SYMBOL(inet_sk_rebuild_header);
 struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 				 netdev_features_t features)
 {
-	bool udpfrag = false, fixedid = false, encap;
+	bool udpfrag = false, fixedid = false, gso_partial, encap;
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	const struct net_offload *ops;
 	unsigned int offset = 0;
@@ -1245,6 +1245,8 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 	if (IS_ERR_OR_NULL(segs))
 		goto out;
 
+	gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
+
 	skb = segs;
 	do {
 		iph = (struct iphdr *)(skb_mac_header(skb) + nhoff);
@@ -1259,9 +1261,13 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 				iph->id = htons(id);
 				id += skb_shinfo(skb)->gso_segs;
 			}
-			tot_len = skb_shinfo(skb)->gso_size +
-				  SKB_GSO_CB(skb)->data_offset +
-				  skb->head - (unsigned char *)iph;
+
+			if (gso_partial)
+				tot_len = skb_shinfo(skb)->gso_size +
+					  SKB_GSO_CB(skb)->data_offset +
+					  skb->head - (unsigned char *)iph;
+			else
+				tot_len = skb->len - nhoff;
 		} else {
 			if (!fixedid)
 				iph->id = htons(id++);
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index ecd1e09dbbf1..96e0efecefa6 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -24,7 +24,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 	__be16 protocol = skb->protocol;
 	u16 mac_len = skb->mac_len;
 	int gre_offset, outer_hlen;
-	bool need_csum, ufo;
+	bool need_csum, ufo, gso_partial;
 
 	if (!skb->encapsulation)
 		goto out;
@@ -69,6 +69,8 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 		goto out;
 	}
 
+	gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
+
 	outer_hlen = skb_tnl_header_len(skb);
 	gre_offset = outer_hlen - tnl_hlen;
 	skb = segs;
@@ -96,7 +98,7 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 		greh = (struct gre_base_hdr *)skb_transport_header(skb);
 		pcsum = (__sum16 *)(greh + 1);
 
-		if (skb_is_gso(skb)) {
+		if (gso_partial) {
 			unsigned int partial_adj;
 
 			/* Adjust checksum to account for the fact that
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 5c5964962d0c..bc68da38ea86 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -90,12 +90,6 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
 		goto out;
 	}
 
-	/* GSO partial only requires splitting the frame into an MSS
-	 * multiple and possibly a remainder.  So update the mss now.
-	 */
-	if (features & NETIF_F_GSO_PARTIAL)
-		mss = skb->len - (skb->len % mss);
-
 	copy_destructor = gso_skb->destructor == tcp_wfree;
 	ooo_okay = gso_skb->ooo_okay;
 	/* All segments but the first should have ooo_okay cleared */
@@ -108,6 +102,13 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
 	/* Only first segment might have ooo_okay set */
 	segs->ooo_okay = ooo_okay;
 
+	/* GSO partial and frag_list segmentation only requires splitting
+	 * the frame into an MSS multiple and possibly a remainder, both
+	 * cases return a GSO skb. So update the mss now.
+	 */
+	if (skb_is_gso(segs))
+		mss *= skb_shinfo(segs)->gso_segs;
+
 	delta = htonl(oldlen + (thlen + mss));
 
 	skb = segs;
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 81f253b6ff36..f9333c963607 100644
--- a/net/ipv4/udp_offload.c
+++ b/net/ipv4/udp_offload.c
@@ -21,7 +21,7 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
 	__be16 new_protocol, bool is_ipv6)
 {
 	int tnl_hlen = skb_inner_mac_header(skb) - skb_transport_header(skb);
-	bool remcsum, need_csum, offload_csum, ufo;
+	bool remcsum, need_csum, offload_csum, ufo, gso_partial;
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	struct udphdr *uh = udp_hdr(skb);
 	u16 mac_offset = skb->mac_header;
@@ -88,6 +88,8 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
 		goto out;
 	}
 
+	gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
+
 	outer_hlen = skb_tnl_header_len(skb);
 	udp_offset = outer_hlen - tnl_hlen;
 	skb = segs;
@@ -117,7 +119,7 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
 		 * will be using a length value equal to only one MSS sized
 		 * segment instead of the entire frame.
 		 */
-		if (skb_is_gso(skb)) {
+		if (gso_partial) {
 			uh->len = htons(skb_shinfo(skb)->gso_size +
 					SKB_GSO_CB(skb)->data_offset +
 					skb->head - (unsigned char *)uh);