net: fix WriteMsgUDPAddrPort addr handling
WriteMsgUDPAddrPort should accept IPv4 target addresses on IPv6 UDP sockets.
An IPv4 target address will be converted to an IPv4-mapped IPv6 address.
Fixes #52264.
Change-Id: Ib9ed4c61fa1289ae7bbc8c4c9de1a9951b647ec0
GitHub-Last-Rev:
6776fdb0a76faa71ebde58f5143fb1ffb3112adf
GitHub-Pull-Request: golang/go#52265
Reviewed-on: https://go-review.googlesource.com/c/go/+/399454
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>