On Thu, 2015-10-22 at 00:14 +0000, Grumbach, Emmanuel wrote:
>
> Well. I guess I should at least check, but even with very small MSS, our
> device supports up to 20 pointers for the same 802.11 packet: 2 are for
> metadata. So basically, so leaves me only 18 pointers. for each MSS I
> need at least 2 (one for the headers and one for the payload), so I will
> have at most 9 of these for one packet, even with a tiny MSS.
>
I did not see in your patch where you made the checks about 18 segs in a
TSO packet ?
> I agree that all this should be added to the code in a comment.
> Speaking of which...
> int tso_count_descs(struct sk_buff *skb)
> {
> /* The Marvell Way */
> return skb_shinfo(skb)->gso_segs * 2 + skb_shinfo(skb)->nr_frags;
> }
>
> What if there is some payload in the header?
> To me it sounds safer to return:
>
> skb_shinfo(skb)->gso_segs * 2 + skb_shinfo(skb)->nr_frags + 1;
>
> or maybe to test if there is some payload in the header and then add 1?
> If there is payload in the header, it should be considered as another
> frag, shouldn't it?
Minimal count is gso_segs (one per MSS)
Then you have to add extra for the cases we have a mss spanning a frag
in skb.
Thats a max of (skb_shinfo(skb)->nr_frags - 1) + (data_in_head() ? 1 :
0);
So I believe formula would be correct.
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