net: various tests failing in Plan 9 with IPv6 turned on

[fhs]

On 9front:

--- FAIL: TestDialerLocalAddr (0.30s)
    dial_test.go:647: tcp4 [::]:0->127.0.0.1: got <nil>; want some error
--- FAIL: TestInterfaceAddrs (0.04s)
    interface_test.go:105: num IPv4 unicast routes = 0; want >0; summary: &{loop:1 other:1}, &{ipv4:0 ipv6:2}
--- FAIL: TestInterfaceUnicastAddrs (0.00s)
    interface_test.go:135: num IPv4 unicast routes = 0; want >0; summary: &{loop:1 other:1}, &{ipv4:0 ipv6:2}
--- FAIL: TestConcurrentPreferGoResolversDial (0.01s)
    lookup_test.go:1008: custom resolver 0 not dialed during lookup
    lookup_test.go:1008: custom resolver 1 not dialed during lookup
net.test 70513: warning: process exceeds 100 file descriptors
--- FAIL: TestListenMulticastUDP (0.00s)
    udpsock_plan9_test.go:39: multicast not working on plan9
FAIL

On 9legacy:

--- FAIL: TestDialerLocalAddr (0.30s)
    dial_test.go:647: tcp4 [::]:0->127.0.0.1: got <nil>; want some error
--- FAIL: TestInterfaceAddrs (0.00s)
    interface_test.go:105: num IPv6 unicast routes = 0; want >0; summary: &{loop:1 other:1}, &{ipv4:2 ipv6:0}
--- FAIL: TestInterfaceUnicastAddrs (0.01s)
    interface_test.go:135: num IPv6 unicast routes = 0; want >0; summary: &{loop:1 other:1}, &{ipv4:2 ipv6:0}
--- FAIL: TestConcurrentPreferGoResolversDial (0.01s)
    lookup_test.go:1008: custom resolver 0 not dialed during lookup
    lookup_test.go:1008: custom resolver 1 not dialed during lookup
net.test 49603: warning: process exceeds 100 file descriptors
--- FAIL: TestListenMulticastUDP (0.01s)
    udpsock_plan9_test.go:39: multicast not working on plan9
FAIL

After adding some detailed error, we see that TestListenMulticastUDP is failing because addmulti mixes IPv4 and IPv6:

udpsock_plan9_test.go:39: multicast not working on plan9: listen udp4 224.0.0.254:0: addmulti fe80::5054:ff:fe12:3456/64: write /net/udp/clone: incompatible multicast/interface ip address

Also, only in 9legacy, announce doesn't like the multicast address:

udpsock_plan9_test.go:39: multicast not working on plan9: listen udp4 224.0.0.254:0: announce udp4 224.0.0.254:0: not a local IP address

I have a CL I'll send out soon.

@gopherbot, please add labels OS-Plan9, Testing, NeedsFix

[gopherbot]

Change https://golang.org/cl/201397 mentions this issue: net: fix multicast and IPv6 related issues on Plan 9