net: allocate res_state entirely in C memory

The linux-amd64-wsl builder was failing because the res_nsearch
implementation was storing pointer to the res_state's own fields
in other fields in the res_state. If the res_state is Go memory, this
looks like pointers to Go pointers. Moving the res_state to C memory
avoids the problem.

The linux-amd64-wsl builder has been fixed a different way by
replacing res_nsearch with res_search on Linux, where it is thread-safe.
But other systems that still need to use res_nsearch (such as macOS)
may run into the same kind of problem, so it is probably still worth
arranging for the res_state to live entirely in C memory.

Fixes #56658 (again).

Change-Id: I58a14e72c866eaceb02ad828854a1f626b9b8e73
Reviewed-on: https://go-review.googlesource.com/c/go/+/448798
Run-TryBot: Russ Cox <rsc@golang.org>
Auto-Submit: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>

0 files changed, 0 insertions, 0 deletions