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GSO: Support partial segmentation offload

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This patch adds support for something I am referring to as GSO partial.
The basic idea is that we can support a broader range of devices for
segmentation if we use fixed outer headers and have the hardware only
really deal with segmenting the inner header.  The idea behind the naming
is due to the fact that everything before csum_start will be fixed headers,
and everything after will be the region that is handled by hardware.

With the current implementation it allows us to add support for the
following GSO types with an inner TSO_MANGLEID or TSO6 offload:
NETIF_F_GSO_GRE
NETIF_F_GSO_GRE_CSUM
NETIF_F_GSO_IPIP
NETIF_F_GSO_SIT
NETIF_F_UDP_TUNNEL
NETIF_F_UDP_TUNNEL_CSUM

In the case of hardware that already supports tunneling we may be able to
extend this further to support TSO_TCPV4 without TSO_MANGLEID if the
hardware can support updating inner IPv4 headers.

Signed-off-by: Alexander Duyck <aduyck@mirantis.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexander Duyck
2016-04-10 21:45:03 -04:00
committed by David S. Miller
parent 1530545ed6
commit 802ab55adc
11 changed files with 151 additions and 24 deletions
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29
net/core/skbuff.c
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@@ -3076,8 +3076,9 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
struct sk_buff *frag_skb = head_skb;
unsigned int offset = doffset;
unsigned int tnl_hlen = skb_tnl_header_len(head_skb);
unsigned int partial_segs = 0;
unsigned int headroom;
unsigned int len;
unsigned int len = head_skb->len;
__be16 proto;
bool csum;
int sg = !!(features & NETIF_F_SG);
@@ -3094,6 +3095,15 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
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 (features & NETIF_F_GSO_PARTIAL) {
partial_segs = len / mss;
mss *= partial_segs;
}
headroom = skb_headroom(head_skb);
pos = skb_headlen(head_skb);
@@ -3281,6 +3291,23 @@ perform_csum_check:
*/
segs->prev = tail;
/* Update GSO info on first skb in partial sequence. */
if (partial_segs) {
int type = skb_shinfo(head_skb)->gso_type;
/* Update type to add partial and then remove dodgy if set */
type |= SKB_GSO_PARTIAL;
type &= ~SKB_GSO_DODGY;
/* Update GSO info and prepare to start updating headers on
* our way back down the stack of protocols.
*/
skb_shinfo(segs)->gso_size = skb_shinfo(head_skb)->gso_size;
skb_shinfo(segs)->gso_segs = partial_segs;
skb_shinfo(segs)->gso_type = type;
SKB_GSO_CB(segs)->data_offset = skb_headroom(segs) + doffset;
}
/* Following permits correct backpressure, for protocols
* using skb_set_owner_w().
* Idea is to tranfert ownership from head_skb to last segment.