[PATCH 3 of 4] QUIC: allowed ngx_quic_frame_sendto() to return NGX_AGAIN

[Sergey Kandaurov]

> On 6 Jul 2023, at 17:57, Roman Arutyunyan <arut at nginx.com> wrote:
> 
> # HG changeset patch
> # User Roman Arutyunyan <arut at nginx.com>
> # Date 1679920727 -14400
> #      Mon Mar 27 16:38:47 2023 +0400
> # Node ID a1ea543d009311765144351b2557c00c8e6445bf
> # Parent  f98ff9b62d2bccac10b603b8183eca2ff0f4183e
> QUIC: allowed ngx_quic_frame_sendto() to return NGX_AGAIN.
> 
> Previously, NGX_AGAIN returned by ngx_send() was treated by
> ngx_quic_frame_sendto() as error, which triggered errors in its callers.
> However, a blocked socket is not an error.  Now NGX_AGAIN is passed as is to
> the ngx_quic_frame_sendto() callers, which can safely ignore it.

Looks good, as a prerequisite for PMTU probes.
Probably, it makes sense to reflect this in the description.

-- 
Sergey Kandaurov