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Paul Marks authored
dialSerial connects to a list of addresses in sequence. If a timeout is specified, then each address gets an equal fraction of the remaining time, with a magic constant (2 seconds) to prevent "dial a million addresses" from allotting zero time to each. Normally, net.Dial passes the DNS stub resolver's output to dialSerial. If an error occurs (like destination/port unreachable), it quickly skips to the next address, but a blackhole in the network will cause the connection to hang until the timeout elapses. This is how UNIXy clients traditionally behave, and is usually sufficient for non-broken networks. The DualStack flag enables dialParallel, which implements Happy Eyeballs by racing two dialSerial goroutines, giving the preferred family a head start (300ms by default). This allows clients to avoid long timeouts when the network blackholes IPv4 xor IPv6. Fixes #8453 Fixes #8455 Fixes #8847 Change-Id: Ie415809c9226a1f7342b0217dcdd8f224ae19058 Reviewed-on: https://go-review.googlesource.com/8768Reviewed-by:
Mikio Hara <mikioh.mikioh@gmail.com> Reviewed-by:
Brad Fitzpatrick <bradfitz@golang.org>
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