#Requires -Version 5.1
<#
    JbTecWiz Support Centre -- generated fix script

    Fault : Gigabit LAN transfers run at a fraction of the speed
    Fix   : Disable the offload features one at a time
    Source: https://jbtecwiz.com/support/win-net-slow-lan

    Run as     : Elevated PowerShell
    Expect     : 20 minutes
    Risk       : medium
    Reversible : yes

    WHEN THIS IS THE RIGHT FIX
    Transfers start fast and collapse -- the signature of a broken offload
    implementation.

    HOW TO UNDO IT
    Enable-NetAdapterLso, Enable-NetAdapterChecksumOffload and
    Enable-NetAdapterRsc restore the defaults; nic-before.txt has the
    original values.

    This script walks the fix one step at a time and asks before each
    one. Steps with no command are things you do yourself -- it prints
    those and waits. Run with -DryRun to print without executing.

    --------------------------------------------------------------------
    NO WARRANTY - USE AT YOUR OWN RISK

    This script is provided by JbTecWiz as-is and with no warranty of any
    kind, express or implied. You run it entirely at your own risk.

    JbTecWiz accepts no liability for any loss or damage arising from its
    use, including but not limited to data loss, downtime, or configuration
    changes that turn out to be wrong for your system.

    You are responsible for reading this script before running it, for
    satisfying yourself that it suits the machine in front of you, and for
    having a working backup first. Some steps cannot be undone.
    --------------------------------------------------------------------
#>

[CmdletBinding()]
param(
    # Print every step and command without running anything.
    [switch]$DryRun,
    # Do not ask before each step. Read the script first if you use this.
    [switch]$Unattended
)

$ErrorActionPreference = 'Stop'
$script:Failed = 0

function Write-Rule { param([string]$Text)
    Write-Host ''
    Write-Host ('-' * 70) -ForegroundColor DarkGray
    if ($Text) { Write-Host $Text -ForegroundColor Cyan }
}

function Show-Prose { param([string]$Text, [string]$Colour = "Gray")
    if (-not $Text) { return }
    $words = $Text -split "\s+"; $line = "  "
    foreach ($w in $words) {
        if (($line.Length + $w.Length) -gt 74) { Write-Host $line -ForegroundColor $Colour; $line = "  " }
        $line += "$w "
    }
    if ($line.Trim()) { Write-Host $line -ForegroundColor $Colour }
}

function Invoke-Step {
    param(
        [int]$Number, [string]$Do, [string]$Why,
        [scriptblock]$Command, [switch]$Manual, [string]$Shell = "powershell"
    )
    Write-Rule "  Step $Number of 4"
    Show-Prose $Do "White"
    if ($Why) { Write-Host ""; Show-Prose $Why "DarkGray" }

    if ($Manual) {
        Write-Host ''
        Write-Host '  -> Do this yourself, then press Enter to carry on.' -ForegroundColor Yellow
        if (-not $Unattended -and -not $DryRun) { [void](Read-Host) }
        return
    }

    Write-Host ''
    foreach ($l in ($Command.ToString().Trim() -split "`n")) {
        Write-Host ("    " + $l.Trim()) -ForegroundColor Green
    }
    Write-Host ''

    if ($DryRun) { Write-Host "  (dry run -- not executed)" -ForegroundColor DarkGray; return }
    if (-not $Unattended) {
        $a = Read-Host "  Run this step? [Y]es / [S]kip / [Q]uit"
        if ($a -match "^[Qq]") { Write-Host "  Stopped at your request."; exit 0 }
        if ($a -match "^[Ss]") { Write-Host "  Skipped." -ForegroundColor DarkGray; return }
    }
    try { & $Command }
    catch {
        $script:Failed++
        Write-Host ("  Step $Number failed: " + $_.Exception.Message) -ForegroundColor Red
        Show-Prose "The rest of the fix may depend on this. Read the write-up before carrying on." "Red"
        if (-not $Unattended) {
            $c = Read-Host "  Carry on anyway? [y/N]"
            if ($c -notmatch "^[Yy]") { exit 1 }
        }
    }
}

Write-Rule
Write-Host '  Gigabit LAN transfers run at a fraction of the speed' -ForegroundColor White
Write-Host '  Disable the offload features one at a time' -ForegroundColor Cyan
Write-Host ''
Write-Host '  Risk: medium   Reversible   20 minutes'
Write-Host ''
Show-Prose 'No warranty. Use at your own risk - JbTecWiz accepts no liability. Read it before you run it, and have a backup.' 'DarkYellow'
Write-Rule

if (-not $Unattended -and -not $DryRun) {
    $go = Read-Host '  Ready? [y/N]'
    if ($go -notmatch "^[Yy]") { Write-Host "  Nothing was changed."; exit 0 }
}

Invoke-Step -Number 1 -Do 'Record the current state so it can be put back exactly.' -Command {
    Get-NetAdapterAdvancedProperty -Name 'Ethernet' | Format-Table DisplayName,DisplayValue | Out-File $env:USERPROFILE\Desktop\nic-before.txt
}

Invoke-Step -Number 2 -Do 'Turn off large send offload, which is the usual culprit.' -Command {
    Disable-NetAdapterLso -Name 'Ethernet'
}

Invoke-Step -Number 3 -Do 'Re-test. If it is still slow, try checksum offload and then receive-side coalescing, restoring each one before trying the next.' -Why 'Changing them all at once fixes the symptom and teaches you nothing. One at a time takes twenty minutes and tells you which setting to document for the rest of the estate.' -Command {
    Disable-NetAdapterChecksumOffload -Name 'Ethernet'
    Disable-NetAdapterRsc -Name 'Ethernet'
}

Invoke-Step -Number 4 -Do 'Update the network driver from the manufacturer, then re-enable everything and test again -- a fixed driver is better than a permanently disabled feature.' -Manual

Write-Rule "  Confirm it worked"
Show-Prose 'A large file copy holds a steady rate for its whole duration.' 'White'
Write-Host ''
if (-not $DryRun) {
    Get-NetAdapterLso -Name 'Ethernet' | Format-Table Name,V1IPv4Enabled,IPv4Enabled
}

Write-Rule
if ($script:Failed -gt 0) {
    Write-Host ("  Finished with " + $script:Failed + " failed step(s).") -ForegroundColor Yellow
    Show-Prose 'Read the full write-up at https://jbtecwiz.com/support/win-net-slow-lan' 'Yellow'
} else {
    Write-Host '  Finished.' -ForegroundColor Green
}
Write-Host ''
Show-Prose 'To undo: Enable-NetAdapterLso, Enable-NetAdapterChecksumOffload and Enable-NetAdapterRsc restore the defaults; nic-before.txt has the original values.' 'DarkGray'
Write-Rule