Pull request: Export default ping timeout

Merge in DNS/dnsproxy from exp-const to master

Updates AdguardTeam/AdGuardHome#1992.

Squashed commit of the following:

commit 65aa4bf
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Fri Aug 27 19:32:50 2021 +0300

    fastip: export the default ping timeout

fastip/fastest.go

@@ -14,6 +14,10 @@ import (
 	"github.com/miekg/dns"
 )
 
+// DefaultPingWaitTimeout is the default period of time for waiting ping
+// operations to finish.
+const DefaultPingWaitTimeout = 1 * time.Second
+
 // FastestAddr provides methods to determine the fastest network addresses.
 type FastestAddr struct {
 	// ipCacheLock protects ipCache.
@@ -44,7 +48,7 @@ func NewFastestAddr() (f *FastestAddr) {
 			EnableLRU: true,
 		}),
 		pingPorts:       []uint{80, 443},
-		PingWaitTimeout: defaultPingWaitTimeout,
+		PingWaitTimeout: DefaultPingWaitTimeout,
 		pinger:          &net.Dialer{Timeout: pingTCPTimeout},
 	}
 }

fastip/ping.go

@@ -8,10 +8,6 @@ import (
 	"github.com/AdguardTeam/golibs/netutil"
 )
 
-// defaultPingWaitTimeout is the default period of time for waiting ping
-// operations to finish.
-const defaultPingWaitTimeout = 1 * time.Second
-
 // pingTCPTimeout is a TCP connection timeout.  It's higher than pingWaitTimeout
 // since the slower connections will be cached anyway.
 const pingTCPTimeout = 4 * time.Second