net: Make Listen(":port") use IPv6 when IPv4 is not supported.
When running an experimental kernel with IPv4 disabled, Listen(":port")
currently tries to create an AF_INET socket, and fails. Instead, it
should see !supportsIPv4, and use an AF_INET6 socket.
This sort of environment is quite esoteric at the moment, but I can
force the tests to fail on regular Linux using the following tweaks:
- net/net.go: supportsIPv4, supportsIPv6, supportsIPv4map = false, true, false
- net/sockopt_linux.go: ipv6only=true
- net/ipsock_posix.go: Revert this fix
- ./make.bash && ../bin/go test net
Also, make the arrows in server_test.go point to the left, because
server<-client is easier to read.
Fixes #12510
Change-Id: I0cc3b6b08d5e6908d2fbf8594f652ba19815aa4b
Reviewed-on: https://go-review.googlesource.com/14334
Run-TryBot: Paul Marks <pmarks@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/net/ipsock_posix.go b/src/net/ipsock_posix.go
index 83eaf85..4419aaf 100644
--- a/src/net/ipsock_posix.go
+++ b/src/net/ipsock_posix.go
@@ -101,10 +101,11 @@
//
// 1. A wild-wild listen, "tcp" + ""
// If the platform supports both IPv6 and IPv6 IPv4-mapping
-// capabilities, we assume that the user want to listen on
-// both IPv4 and IPv6 wildcard address over an AF_INET6
-// socket with IPV6_V6ONLY=0. Otherwise we prefer an IPv4
-// wildcard address listen over an AF_INET socket.
+// capabilities, or does not support IPv4, we assume that
+// the user wants to listen on both IPv4 and IPv6 wildcard
+// addresses over an AF_INET6 socket with IPV6_V6ONLY=0.
+// Otherwise we prefer an IPv4 wildcard address listen over
+// an AF_INET socket.
//
// 2. A wild-ipv4wild listen, "tcp" + "0.0.0.0"
// Same as 1.
@@ -137,7 +138,7 @@
}
if mode == "listen" && (laddr == nil || laddr.isWildcard()) {
- if supportsIPv4map {
+ if supportsIPv4map || !supportsIPv4 {
return syscall.AF_INET6, false
}
if laddr == nil {
