On 08/19/2015 05:18 PM, Eric Dumazet wrote:

On Wed, 2015-08-19 at 15:59 +0300, Emmanuel Grumbach wrote:

quoted

The segmentation is done completely in software. The
driver creates several MPDUs out of a single large send.
Each MPDU is a newly allocated SKB.
A page is allocated to create the headers that need to be
duplicated (SNAP / IP / TCP). The WiFi header is in the
header of the newly created SKBs.

type=feature

Change-Id: I238ffa79cacc5bbdacdfbf3e9673c8d4f02b462a
Signed-off-by: Emmanuel Grumbach <redacted>
---
 drivers/net/wireless/iwlwifi/mvm/tx.c | 513 +++++++++++++++++++++++++++++++---
 1 file changed, 481 insertions(+), 32 deletions(-)

Ouch dynamic allocations while doing xmit are certainly not needed.
Your driver should pre-allocated space for headers.

This is right as long as you don't need *several* headers in one single
skb. In the case of A-MSDU, I need to have several TCP / IP / SNAP
headers in the same skb. At least that's how my HW layer in the driver
is built. See the other thread.

Drivers willing to implement tso have to use net/core/tso.c provided
helpers.

$ git grep -n tso_build_hdr
drivers/net/ethernet/cavium/thunder/nicvf_queues.c:1030:                tso_build_hdr(skb, hdr, &tso, data_left, total_len == 0);
drivers/net/ethernet/freescale/fec_main.c:729:          tso_build_hdr(skb, hdr, &tso, data_left, total_len == 0);
drivers/net/ethernet/marvell/mv643xx_eth.c:842:         tso_build_hdr(skb, hdr, &tso, data_left, total_len == 0);
drivers/net/ethernet/marvell/mvneta.c:1650:             tso_build_hdr(skb, hdr, &tso, data_left, total_len == 0);
include/net/tso.h:15:void tso_build_hdr(struct sk_buff *skb, char *hdr, struct tso_t *tso,
net/core/tso.c:14:void tso_build_hdr(struct sk_buff *skb, char *hdr, struct tso_t *tso,
net/core/tso.c:37:EXPORT_SYMBOL(tso_build_hdr);

This looks promising indeed. I'll take a close look.
Thanks a bunch.
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