curl / Mailing Lists / curl-library / Single Mail


Re: unexpected code 35 (if tcp listen backlog is full)

From: Michael Kilburn via curl-library <>
Date: Sun, 14 Jan 2018 22:29:10 -0600

On Sun, Jan 14, 2018 at 4:02 PM, Daniel Stenberg <> wrote:

> On Sun, 14 Jan 2018, Michael Kilburn wrote:
> this:
>> -linux.html suggests it is possible -- if accept queue is full, ACK gets
>> discarded while from client perspective connection is established and it
>> will start sending data (initiating TLS handshake). And eventual RST from
>> server (because it could not acknowledge resent ACKs due to full accept
>> queue) will cause connection drop while libcurl TLS logic waits for
>> response. Do you think this is what happens? Can code 35 be returned in
>> this situation?
> It seems like a plausible scenario, yes!

Well, disregard my report then, please.

If I am to use my own cache of easy handles -- how it is going to work wrt
>> TLS? Afair, TLS handshake needs to be renewed/renegotiated on regular basis
>> -- what if my handle wasn't used for 10 mins? 2 hours?
> libcurl will handle that for you transparently. You should always be able
> to re-use an existing easy handle for subsequent requests. Also, if you use
> the multi interface, the connection pool is actually owned/held by the
> multi handle so then re-using easy handles isn't that important.

Thank you, Daniel.

Received on 2018-01-15