Date:   Tue, 23 Aug 2016 07:20:30 +0200
From:   Steffen Klassert <steffen.klassert@...unet.com>
To:     <netdev@...r.kernel.org>
CC:     Eric Dumazet <eric.dumazet@...il.com>,
        Alexander Duyck <alexander.h.duyck@...el.com>
Subject: [PATCH net-next v1] 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@...unet.com>
---
 net/core/skbuff.c      | 89 +++++++++++++++++++++++++++++++++++++++++++++++++-
 net/ipv4/af_inet.c     |  7 ++--
 net/ipv4/gre_offload.c |  7 +++-
 net/ipv4/tcp_offload.c |  3 ++
 net/ipv4/udp_offload.c |  9 +++--
 net/ipv6/ip6_offload.c |  6 +++-
 6 files changed, 114 insertions(+), 7 deletions(-)

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 3864b4b6..a614e9d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3078,6 +3078,92 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
 	sg = !!(features & NETIF_F_SG);
 	csum = !!can_checksum_protocol(features, proto);
 
+	headroom = skb_headroom(head_skb);
+
+	if (list_skb && net_gso_ok(features, skb_shinfo(head_skb)->gso_type) &&
+	    csum && sg && (mss != GSO_BY_FRAGS) &&
+	    !(features & NETIF_F_GSO_PARTIAL)) {
+		unsigned int lskb_segs;
+		unsigned int delta_segs, delta_len, delta_truesize;
+		struct sk_buff *nskb;
+		delta_segs = delta_len = delta_truesize = 0;
+
+		segs = __alloc_skb(skb_headlen(head_skb) + headroom,
+				   GFP_ATOMIC, skb_alloc_rx_flag(head_skb),
+				   NUMA_NO_NODE);
+		if (unlikely(!segs))
+			return ERR_PTR(-ENOMEM);
+
+		skb_reserve(segs, headroom);
+		skb_put(segs, skb_headlen(head_skb));
+		skb_copy_from_linear_data(head_skb, segs->data, segs->len);
+		copy_skb_header(segs, head_skb);
+
+		if (skb_shinfo(head_skb)->nr_frags) {
+			int i;
+
+			if (skb_orphan_frags(head_skb, GFP_ATOMIC))
+				goto err;
+
+			for (i = 0; i < skb_shinfo(head_skb)->nr_frags; i++) {
+				skb_shinfo(segs)->frags[i] = skb_shinfo(head_skb)->frags[i];
+				skb_frag_ref(head_skb, i);
+			}
+			skb_shinfo(segs)->nr_frags = i;
+		}
+
+		do {
+			nskb = skb_clone(list_skb, GFP_ATOMIC);
+			if (unlikely(!nskb))
+				goto err;
+
+			list_skb = list_skb->next;
+
+			if (!tail)
+				segs->next = nskb;
+			else
+				tail->next = nskb;
+
+			tail = nskb;
+
+			if (skb_cow_head(nskb, doffset + headroom))
+				goto err;
+
+			lskb_segs = nskb->len / mss;
+
+			skb_shinfo(nskb)->gso_size = mss;
+			skb_shinfo(nskb)->gso_type = skb_shinfo(head_skb)->gso_type;
+			skb_shinfo(nskb)->gso_segs = lskb_segs;
+
+
+			delta_segs += lskb_segs;
+			delta_len += nskb->len;
+			delta_truesize += nskb->truesize;
+
+			__skb_push(nskb, doffset);
+
+			skb_release_head_state(nskb);
+			__copy_skb_header(nskb, head_skb);
+
+			skb_headers_offset_update(nskb, skb_headroom(nskb) - headroom);
+			skb_reset_mac_len(nskb);
+
+			skb_copy_from_linear_data_offset(head_skb, -tnl_hlen,
+							 nskb->data - tnl_hlen,
+							 doffset + tnl_hlen);
+
+		} while (list_skb);
+
+		skb_shinfo(segs)->gso_segs -= delta_segs;
+		segs->len = head_skb->len - delta_len;
+		segs->data_len = head_skb->data_len - delta_len;
+		segs->truesize += head_skb->data_len - delta_truesize;
+
+		segs->prev = tail;
+
+		goto out;
+	}
+
 	/* GSO partial only requires that we trim off any excess that
 	 * doesn't fit into an MSS sized block, so take care of that
 	 * now.
@@ -3090,7 +3176,6 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
 			partial_segs = 0;
 	}
 
-	headroom = skb_headroom(head_skb);
 	pos = skb_headlen(head_skb);
 
 	do {
@@ -3307,6 +3392,8 @@ perform_csum_check:
 		swap(tail->destructor, head_skb->destructor);
 		swap(tail->sk, head_skb->sk);
 	}
+
+out:
 	return segs;
 
 err:
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 55513e6..c814afa 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1195,7 +1195,7 @@ 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 = false, encap;
 	struct sk_buff *segs = ERR_PTR(-EINVAL);
 	const struct net_offload *ops;
 	unsigned int offset = 0;
@@ -1248,6 +1248,9 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 	if (IS_ERR_OR_NULL(segs))
 		goto out;
 
+	if (skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL)
+		gso_partial = true;
+
 	skb = segs;
 	do {
 		iph = (struct iphdr *)(skb_mac_header(skb) + nhoff);
@@ -1257,7 +1260,7 @@ struct sk_buff *inet_gso_segment(struct sk_buff *skb,
 				iph->frag_off |= htons(IP_MF);
 			offset += skb->len - nhoff - ihl;
 			tot_len = skb->len - nhoff;
-		} else if (skb_is_gso(skb)) {
+		} else if (skb_is_gso(skb) && gso_partial) {
 			if (!fixedid) {
 				iph->id = htons(id);
 				id += skb_shinfo(skb)->gso_segs;
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index ecd1e09..cf82e28 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 +69,11 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
 		goto out;
 	}
 
+	if (skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL)
+		gso_partial = true;
+	else
+		gso_partial = false;
+
 	outer_hlen = skb_tnl_header_len(skb);
 	gre_offset = outer_hlen - tnl_hlen;
 	skb = segs;
diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
index 5c59649..dddd227 100644
--- a/net/ipv4/tcp_offload.c
+++ b/net/ipv4/tcp_offload.c
@@ -107,6 +107,9 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
 
 	/* Only first segment might have ooo_okay set */
 	segs->ooo_okay = ooo_okay;
+	if (skb_is_gso(segs) && !(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL))
+		mss = (skb_tail_pointer(segs) - skb_transport_header(segs)) +
+		       segs->data_len - thlen;
 
 	delta = htonl(oldlen + (thlen + mss));
 
diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
index 81f253b..dfb6a2c 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 +88,11 @@ static struct sk_buff *__skb_udp_tunnel_segment(struct sk_buff *skb,
 		goto out;
 	}
 
+	if (skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL)
+		gso_partial = true;
+	else
+		gso_partial = false;
+
 	outer_hlen = skb_tnl_header_len(skb);
 	udp_offset = outer_hlen - tnl_hlen;
 	skb = segs;
@@ -117,7 +122,7 @@ 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 (skb_is_gso(skb) && gso_partial) {
 			uh->len = htons(skb_shinfo(skb)->gso_size +
 					SKB_GSO_CB(skb)->data_offset +
 					skb->head - (unsigned char *)uh);
diff --git a/net/ipv6/ip6_offload.c b/net/ipv6/ip6_offload.c
index 22e90e5..0ec16ba 100644
--- a/net/ipv6/ip6_offload.c
+++ b/net/ipv6/ip6_offload.c
@@ -69,6 +69,7 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 	int offset = 0;
 	bool encap, udpfrag;
 	int nhoff;
+	bool gso_partial = false;
 
 	skb_reset_network_header(skb);
 	nhoff = skb_network_header(skb) - skb_mac_header(skb);
@@ -101,9 +102,12 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
 	if (IS_ERR(segs))
 		goto out;
 
+	if (skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL)
+		gso_partial = true;
+
 	for (skb = segs; skb; skb = skb->next) {
 		ipv6h = (struct ipv6hdr *)(skb_mac_header(skb) + nhoff);
-		if (skb_is_gso(skb))
+		if (skb_is_gso(skb) && gso_partial)
 			payload_len = skb_shinfo(skb)->gso_size +
 				      SKB_GSO_CB(skb)->data_offset +
 				      skb->head - (unsigned char *)(ipv6h + 1);
-- 
1.9.1

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