Re: [PATCH net-next v4 2/3] sock: support SO_PRIORITY cmsg

[Willem de Bruijn <willemdebruijn.kernel@gmail.com>]

Anna Emese Nyiri wrote:
> The Linux socket API currently allows setting SO_PRIORITY at the
> socket level, applying a uniform priority to all packets sent through
> that socket. The exception to this is IP_TOS, when the priority value
> is calculated during the handling of
> ancillary data, as implemented in commit <f02db315b8d88>
> ("ipv4: IP_TOS and IP_TTL can be specified as ancillary data").
> However, this is a computed
> value, and there is currently no mechanism to set a custom priority
> via control messages prior to this patch.
> 
> According to this patch, if SO_PRIORITY is specified as ancillary data,
> the packet is sent with the priority value set through
> sockc->priority, overriding the socket-level values
> set via the traditional setsockopt() method. This is analogous to
> the existing support for SO_MARK, as implemented in commit
> <c6af0c227a22> ("ip: support SO_MARK cmsg").
> 
> If both cmsg SO_PRIORITY and IP_TOS are passed, then the one that
> takes precedence is the last one in the cmsg list.
> 
> This patch has the side effect that raw_send_hdrinc now interprets cmsg
> IP_TOS.
> 
> Suggested-by: Ferenc Fejes <fejes@inf.elte.hu>
> Signed-off-by: Anna Emese Nyiri <annaemesenyiri@gmail.com>

Reviewed-by: Willem de Bruijn <willemb@google.com>

Good catch on ipv6 ping.