内置 lookup 函数跳过下发 fakeip #2182

Job	Run time
Debug build	31s
Debug build (Go 1.20)	54s
Debug build (Go 1.18)	29s
cross (windows-amd64, windows, amd64, v1)	56s
cross (windows-amd64-v3, windows, amd64, v3)	1m 14s
cross (windows-386, windows, 386)	36s
cross (windows-arm64, windows, arm64)	1m 5s
cross (windows-arm32v7, windows, arm, 7)	40s
cross (linux-amd64, linux, amd64, v1)	3m 0s
cross (linux-amd64-v3, linux, amd64, v3)	1m 7s
cross (linux-386, linux, 386)	1m 9s
cross (linux-arm64, linux, arm64)	1m 2s
cross (linux-armv5, linux, arm, 5)	37s
cross (linux-armv6, linux, arm, 6)	37s
cross (linux-armv7, linux, arm, 7)	39s
cross (linux-mips-softfloat, linux, mips, softfloat)	1m 18s
cross (linux-mips-hardfloat, linux, mips, hardfloat)	1m 3s
cross (linux-mipsel-softfloat, linux, mipsle, softfloat)	1m 23s
cross (linux-mipsel-hardfloat, linux, mipsle, hardfloat)	44s
cross (linux-mips64, linux, mips64)	1m 7s
cross (linux-mips64el, linux, mips64le)	39s
cross (linux-s390x, linux, s390x)	39s
cross (darwin-amd64, darwin, amd64, v1)	54s
cross (darwin-amd64-v3, darwin, amd64, v3)	1m 7s
cross (darwin-arm64, darwin, arm64)	1m 18s
cross (freebsd-amd64, freebsd, amd64, v1)	1m 12s
cross (freebsd-amd64-v3, freebsd, amd64, v3)	1m 0s
cross (freebsd-386, freebsd, 386)	38s
cross (freebsd-arm64, freebsd, arm64)	58s
	28m 36s

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