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Date: Thu, 25 Aug 2016 13:00:19 +0200
From: Steffen Klassert <steffen.klassert@...unet.com>
To: Alexander Duyck <alexander.duyck@...il.com>
CC: Netdev <netdev@...r.kernel.org>,
Eric Dumazet <eric.dumazet@...il.com>,
Alexander Duyck <alexander.h.duyck@...el.com>,
Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Subject: Re: [PATCH net-next v1] gso: Support partial splitting at the
frag_list pointer
On Wed, Aug 24, 2016 at 09:27:54AM -0700, Alexander Duyck wrote:
>
> In you case though we maybe be able to make this easier. If I am not
> mistaken I believe we should have the main skb, and any in the chain
> excluding the last containing the same amount of data.
Yes, it seems to be like that. With this observation we can spmplify
things.
> That being the
> case we should be able to determine the size that you would need to
> segment at by taking skb->len, and removing the length of all the
> skbuffs hanging off of frag_list. At that point you just use that as
> your MSS for segmentation and it should break things up so that you
> have a series of equal sized segments split as the frag_list buffer
> boundaries.
>
> After that all that is left is to update the gso info for the buffers.
> For GSO_PARTIAL I was handling that on the first segment only. For
> this change you would need to update that code to address the fact
> that you would have to determine the number of segments on the first
> frame and the last since the last could be less than the first, but
> all of the others in-between should have the same number of segments.
I tried to do this and ended up with the patch below.
Seems to work, but sill needs some tests. So it is
not an official patch submission.
Subject: [PATCH net-next RFC] 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 | 46 ++++++++++++++++++++++++++++++++++++----------
net/ipv4/af_inet.c | 6 ++++--
net/ipv4/gre_offload.c | 4 +++-
net/ipv4/tcp_offload.c | 3 +++
net/ipv4/udp_offload.c | 6 ++++--
net/ipv6/ip6_offload.c | 5 ++++-
6 files changed, 54 insertions(+), 16 deletions(-)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 3864b4b6..cb326e5 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3060,6 +3060,7 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
unsigned int offset = doffset;
unsigned int tnl_hlen = skb_tnl_header_len(head_skb);
unsigned int partial_segs = 0;
+ unsigned int fraglist_segs = 0;
unsigned int headroom;
unsigned int len = head_skb->len;
__be16 proto;
@@ -3078,16 +3079,27 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
sg = !!(features & NETIF_F_SG);
csum = !!can_checksum_protocol(features, proto);
- /* 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.
- */
- if (sg && csum && (features & NETIF_F_GSO_PARTIAL)) {
- partial_segs = len / mss;
- if (partial_segs > 1)
- mss *= partial_segs;
- else
- partial_segs = 0;
+ if (sg && csum) {
+ /* 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.
+ */
+ if ((features & NETIF_F_GSO_PARTIAL)) {
+ partial_segs = len / mss;
+ if (partial_segs > 1)
+ mss *= partial_segs;
+ else
+ partial_segs = 0;
+ } else if (list_skb && (mss != GSO_BY_FRAGS) &&
+ net_gso_ok(features, skb_shinfo(head_skb)->gso_type)) {
+
+ skb_walk_frags(head_skb, segs) {
+ len -= segs->len;
+ }
+ fraglist_segs = len / mss;
+ mss = len;
+ segs = NULL;
+ }
}
headroom = skb_headroom(head_skb);
@@ -3298,6 +3310,20 @@ perform_csum_check:
SKB_GSO_CB(segs)->data_offset = skb_headroom(segs) + doffset;
}
+ if (fraglist_segs) {
+ struct sk_buff *iter;
+
+ for (iter = segs; iter; iter = iter->next) {
+ if (iter->next) {
+ skb_shinfo(iter)->gso_size = skb_shinfo(head_skb)->gso_size;
+ skb_shinfo(iter)->gso_segs = fraglist_segs;
+ } else {
+ skb_shinfo(iter)->gso_size = skb_shinfo(head_skb)->gso_size;
+ skb_shinfo(iter)->gso_segs = iter->len / skb_shinfo(head_skb)->gso_size;
+ }
+ }
+ }
+
/* Following permits correct backpressure, for protocols
* using skb_set_owner_w().
* Idea is to tranfert ownership from head_skb to last segment.
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 989a362..ac46233 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1190,7 +1190,7 @@ 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;
@@ -1243,6 +1243,8 @@ 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);
@@ -1252,7 +1254,7 @@ 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..7c56785 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;
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..0b909f9 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 (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..73dd0d1 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;
skb_reset_network_header(skb);
nhoff = skb_network_header(skb) - skb_mac_header(skb);
@@ -101,9 +102,11 @@ static struct sk_buff *ipv6_gso_segment(struct sk_buff *skb,
if (IS_ERR(segs))
goto out;
+ gso_partial = !!(skb_shinfo(segs)->gso_type & SKB_GSO_PARTIAL);
+
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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