env/darwin/aws: switch to vmnet-shared networking

This networking mode, which uses a virtualization networking API from
Apple, appears to be more stable than the default userspace networking.

Multiple guests will share the same subnet, so they must have different
MAC addresses.

Apple's API seems to run an DNS server that serves compressed SRV
records, which Go does not support (golang/go#36718) and thus causes a
net test to fail. Until that is resolved, we must manually specify a
custom DNS server.

For golang/go#48945.
Updates golang/go#36718.

Change-Id: Ibc5b91ed1456d1364975febe83fd282c42bd6ed1
Reviewed-on: https://go-review.googlesource.com/c/build/+/442255
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Jenny Rakoczy <[email protected]>
Run-TryBot: Michael Pratt <[email protected]>

Author: prattmic

env/darwin/aws/README.md

@@ -126,8 +126,9 @@ configure it to autoboot to macOS.
 $ $HOME/start-mutable.sh macos-monterey.qcow2 $OSK_VALUE
 ```
 
-Now complete the remainder of the [machine setup](../setup-notes.md). See the
-`hostfwd` option in `qemu.sh` if you would like SSH access to the guest.
+Now complete the remainder of the [machine setup](../setup-notes.md). For SSH
+access, the guest should be reachable at 192.168.1.2 or 192.168.1.3 from the
+host machine.
 
 Copy complete images to `s3://go-builder-data/darwin/` for use on other
 builders.

env/darwin/aws/qemu.sh

@@ -35,13 +35,13 @@ args=(
   -device ich9-ahci,id=sata
   -drive id=MacHDD,if=none,format=qcow2,file="$DISK"
   -device ide-hd,bus=sata.2,drive=MacHDD
-  -netdev user,id=net0 # add ,hostfwd=tcp::5555-:22 to forward SSH to localhost:5555.
-  -device virtio-net-pci,netdev=net0,id=net0,mac=52:54:00:c9:18:27 # for macOS >= 11
-  # -device vmxnet3,netdev=net0,id=net0,mac=52:54:00:c9:18:27 # for macOS < 11
+  -netdev vmnet-shared,id=net0
+  -device virtio-net-pci,netdev=net0,id=net0,mac=52:54:00:c9:18:0$PORT # for macOS >= 11
+  # -device vmxnet3,netdev=net0,id=net0,mac=52:54:00:c9:18:0$PORT # for macOS < 11
   -monitor stdio
   -device VGA,vgamem_mb=128
   -M accel=hvf
   -display vnc=127.0.0.1:"$PORT"
 )
 
-DYLD_LIBRARY_PATH="$HOME/sysroot-macos-x86_64/lib" "$HOME/sysroot-macos-x86_64/bin/qemu-system-x86_64" "${args[@]}" ${EXTRA_ARGS:+$EXTRA_ARGS}
+sudo env DYLD_LIBRARY_PATH="$HOME/sysroot-macos-x86_64/lib" "$HOME/sysroot-macos-x86_64/bin/qemu-system-x86_64" "${args[@]}" ${EXTRA_ARGS:+$EXTRA_ARGS}

env/darwin/setup-notes.md

@@ -107,6 +107,9 @@ In System Preferences:
 - Sharing > enable ssh (leave the default administrators setting)
 - Users & Groups > Gopher Gopherson > Login Items > add run-builder
 - Users & Groups > Login Options > auto-login Gopher Gopherson
+- Network -> Ethernet -> Advanced -> DNS -> Add DNS server -> 8.8.8.8
+  - Only necessary on AWS guests, and until https://go.dev/issue/36718 is
+    resolved on all tested releases.
 
 Install XCode:
 - Download Xcode from the Apple Developer site: