On Mon, Dec 21, 2020 at 7:46 PM Eric Dumazet [off-list ref] wrote:

quoted

On Sat, Dec 19, 2020 at 5:55 PM Ben Greear [off-list ref] wrote:

quoted

On 12/19/20 7:18 AM, Johannes Berg wrote:

quoted

On Fri, 2020-12-18 at 12:16 -0800, Jakub Kicinski wrote:

quoted

On Thu, 17 Dec 2020 12:40:26 -0800 Ben Greear wrote:

quoted

On 12/17/20 10:20 AM, Eric Dumazet wrote:

quoted

On Thu, Dec 17, 2020 at 7:13 PM Ben Greear [off-list ref] wrote:

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It is the iwlwifi/mvm logic that supports ax200.

Let me ask again :

I see two different potential call points :

drivers/net/wireless/intel/iwlwifi/pcie/tx.c:1529:
tso_build_hdr(skb, hdr_page->pos, &tso, data_left, !total_len);
drivers/net/wireless/intel/iwlwifi/queue/tx.c:427:
tso_build_hdr(skb, hdr_page->pos, &tso, data_left, !total_len);

To the best of your knowledge, which one would be used in your case ?

Both are horribly complex, I do not want to spend time studying two
implementations.

It is the queue/tx.c code that executes on my system, verified with
printk.

Not sure why Intel's not on CC here.

Heh :)

Let's also add linux-wireless.

quoted

Luca, is the ax200 TSO performance regression with recent kernel on your
radar?

It wasn't on mine for sure, so far. But it's supposed to be Christmas
vacation, so haven't checked our bug tracker etc. I see Emmanuel was at
least looking at the bug report, but not sure what else happened yet.

Not to bitch and moan too much, but even the most basic of testing would
have shown this, how can testing be so poor on the ax200 driver?

It even shows up with the out-of-tree ax200 driver.

quoted

Off the top of my head, I don't really see the issue. Does anyone have
the ability to capture the frames over the air (e.g. with another AX200
in monitor mode, load the driver with amsdu_size=3 module parameter to
properly capture A-MSDUs)?

I can do that at some point, and likely it could be reproduced with an /n or /ac
AP and those are a lot easier to sniff.

Thanks,
Ben


--
Ben Greear [off-list ref]
Candela Technologies Inc  http://www.candelatech.com

It seems the problem comes from some skbs reaching the driver with
gso_type == 0,
meaning skb_is_gso_tcp() is fuzzy. (net/core/tso.c is only one of the
skb_is_gso_tcp() users)

Local TCP stack should provide either SKB_GSO_TCPV4 or SKB_GSO_TCPV6
for GSO packets.

So maybe the issue is coming from traffic coming from a VM through a
tun device or something,
and our handling of GSO_ROBUST / DODGY never cared about setting
SKB_GSO_TCPV4 or SKB_GSO_TCPV6 if not already given by user space ?

Or a plain bug somewhere, possibly overwriting  gso_type with 0 or garbage...

Oh well, iwl_mvm_tx_tso_segment() 'builds' a fake gso packet.

I suspect this will fix the issue :

diff --git a/drivers/net/wireless/intel/iwlwifi/mvm/tx.c

b/drivers/net/wireless/intel/iwlwifi/mvm/tx.c
index a983c215df310776ffe67f3b3ffa203eab609bfc..e7ad6367c88de4aff700c630d850760d1d3bf011
100644

--- a/drivers/net/wireless/intel/iwlwifi/mvm/tx.c
+++ b/drivers/net/wireless/intel/iwlwifi/mvm/tx.c

@@ -773,6 +773,7 @@ iwl_mvm_tx_tso_segment(struct sk_buff *skb,

unsigned int num_subframes,

        next = skb_gso_segment(skb, netdev_flags);
        skb_shinfo(skb)->gso_size = mss;
+       skb_shinfo(skb)->gso_type = ipv4 ? SKB_GSO_TCPV4 : SKB_GSO_TCPV6;
        if (WARN_ON_ONCE(IS_ERR(next)))
                return -EINVAL;
        else if (next)