[libav-devel] [PATCH 1/2] network: Add RFC 8305 style "Happy Eyeballs"/"Fast Fallback" helper function

Martin Storsjö martin at martin.st
Fri Aug 31 11:31:32 CEST 2018

On Wed, 22 Aug 2018, Luca Barbato wrote:

> On 21/08/2018 09:29, Martin Storsjö wrote:
>> For cases with dual stack (IPv4 + IPv6) connectivity, but where one
>> stack potentially is less reliable, strive to trying to connect over
>> both protocols in parallel, using whichever address connected first.
>> In cases with a hostname resolving to multiple IPv4 and IPv6
>> addresses, the current connection mechanism would try all addresses
>> in the order returned by getaddrinfo (with all IPv6 addresses ordered
>> before the IPv4 addresses normally). If connection attempts to the
>> IPv6 addresses return quickly with an error, this was no problem, but
>> if they were unsuccessful leading up to timeouts, the connection process
>> would have to wait for timeouts on all IPv6 target addresses before
>> attempting any IPv4 address.
>> Similar to what RFC 8305 suggests, reorder the list of addresses to
>> try connecting to, interleaving address families. After starting one
>> connection attempt, start another one in parallel after a small delay
>> (200 ms as suggested by the RFC).
>> For cases with unreliable IPv6 but reliable IPv4, this should make
>> connection attempts work as reliably as with plain IPv4, with only an
>> extra 200 ms of connection delay.
> The set looks fine to me.


// Martin

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