netdev - Re: [PATCH net] udp: consistently apply ufo or fragmentation

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Date:   Mon, 14 Aug 2017 10:53:10 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Vasily Averin <vvs@...tuozzo.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH net] udp: consistently apply ufo or fragmentation

> ip*_ufo_append_data() is called now for each skb_is_gso() packet.
> Before the patch it was called for UDP packets only.
>
> Could you please clarify, is it correct?

__ip_append_data is called for udp, raw, icmp and ping sockets.
Of these, only udp packets have a path to get skb_is_gso() set:
when __ip_append_data has been called before on this packet
(using MSG_MORE) and the path entered ip_ufo_append_data
in that call through the other conditions in the branch, which
include sk->sk_type == SOCK_DGRAM.

This function is not reached from other segmentable protocols
like tcp, which call ip_queue_xmit in the ip layer. The exceptions
are sending in ip_send_unicast_reply, but those will not have gso.