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Re: [lwip-users] lwipopts: TX_SINGLE_PBUF
From: |
Simon Goldschmidt |
Subject: |
Re: [lwip-users] lwipopts: TX_SINGLE_PBUF |
Date: |
Fri, 20 Oct 2017 14:42:54 +0200 |
David Gauchard wrote:
> There are two comments in opt.h:
> "@todo: TCP and IP-frag do not work with this, yet:" next to
> LWIP_NETIF_TX_SINGLE_PBUF
> "Try to create unfragmented TCP packets" next to TCP_OVERSIZE
>
> Is there anything planned to get rid of the "todo" and "try" in the above
> comments ?
The whole point of LWIP_NETIF_TX_SINGLE_PBUF was that the stack tries to do its
best.
A driver should still be prepared to get chained pbufs and copy them into one
piece.
LWIP_NETIF_TX_SINGLE_PBUF should be a performance optmization to e.g. prevent
copying
data into a chained pbuf when we know it has to be copied again later to create
a pbuf
in one piece. Where this doesn't hurt much, I don't currently see a problem to
make the
driver do this.
You should be able to just use pbuf_clone() if p->next != NULL.
Of course I'm open to fix the possibly remaining chained pbuf issues, but I
can't
afford the time for this currently.
Simon