Fix resolv.conf in Windows Subsystem for Linux, when WSL doesn't correctly generate it.

wsl-fix-netipinterfaces.ps1

Get-NetAdapter | Where-Object {$_.InterfaceDescription -Match "Cisco AnyConnect"} | Set-NetIPInterface -InterfaceMetric 4000
Get-NetIPInterface -InterfaceAlias "vEthernet (WSL)" | Set-NetIPInterface -InterfaceMetric 1

wsl-fix-resolvconf.sh

#!/bin/bash

TMP=`mktemp`
trap ctrlC INT

removeTempFiles() {
        rm -f $TMP
}

ctrlC() {
        echo
        echo "Trapped Ctrl-C, removing temporary files"
        removeTempFiles
        stty sane
}

echo "Current resolv.conf"
echo "-------------------"
cat /etc/resolv.conf

echo
echo "Creating new resolv.conf"
echo "------------------------"

PSCMD='Get-DnsClientServerAddress -AddressFamily ipv4 | Where-Object { (Get-NetAdapter | Where-Object {$_.Status -Match "Up"} | Select-Object -ExpandProperty ifIndex) -contains $_.InterfaceIndex } | select -ExpandProperty ServerAddresses'
{
        head -1 /etc/resolv.conf | grep '^#.*generated'
        for i in `/mnt/c/Windows/System32/WindowsPowerShell/v1.0/powershell.exe -Command "$PSCMD"`; do
                echo nameserver $i
        done
        tail -n+2 /etc/resolv.conf | grep -v '^nameserver'
} | tr -d '\r' | tee $TMP

echo

(set -x; sudo cp -i $TMP /etc/resolv.conf)

removeTempFiles