diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/net/dial.go | 23 |
1 files changed, 16 insertions, 7 deletions
diff --git a/src/net/dial.go b/src/net/dial.go index b1a5ca7cd5..76dcdc164c 100644 --- a/src/net/dial.go +++ b/src/net/dial.go @@ -44,16 +44,23 @@ type Dialer struct { // If nil, a local address is automatically chosen. LocalAddr Addr - // DualStack enables RFC 6555-compliant "Happy Eyeballs" - // dialing when the network is "tcp" and the host in the - // address parameter resolves to both IPv4 and IPv6 addresses. - // This allows a client to tolerate networks where one address - // family is silently broken. + // DualStack previously enabled RFC 6555 Fast Fallback + // support, also known as "Happy Eyeballs", in which IPv4 is + // tried soon if IPv6 appears to be misconfigured and + // hanging. + // + // Deprecated: Fast Fallback is enabled by default. To + // disable, set FallbackDelay to a negative value. DualStack bool // FallbackDelay specifies the length of time to wait before - // spawning a fallback connection, when DualStack is enabled. + // spawning a RFC 6555 Fast Fallback connection. That is, this + // is the amount of time to wait for IPv6 to succeed before + // assuming that IPv6 is misconfigured and falling back to + // IPv4. + // // If zero, a default delay of 300ms is used. + // A negative value disables Fast Fallback support. FallbackDelay time.Duration // KeepAlive specifies the keep-alive period for an active @@ -81,6 +88,8 @@ type Dialer struct { Control func(network, address string, c syscall.RawConn) error } +func (d *Dialer) dualStack() bool { return d.FallbackDelay >= 0 } + func minNonzeroTime(a, b time.Time) time.Time { if a.IsZero() { return b @@ -393,7 +402,7 @@ func (d *Dialer) DialContext(ctx context.Context, network, address string) (Conn } var primaries, fallbacks addrList - if d.DualStack && network == "tcp" { + if d.dualStack() && network == "tcp" { primaries, fallbacks = addrs.partition(isIPv4) } else { primaries = addrs |