From 4c7671b396f01da0ccbf9f5e71343bf2e90690a8 Mon Sep 17 00:00:00 2001
From: AliveDevil <AliveDevil@users.noreply.github.com>
Date: Wed, 29 Nov 2023 22:59:12 +0100
Subject: [PATCH] Dhcp4 parser

---
 src/pdns-dhcp/Kea/KeaDhcp4Lease.cs        | 72 ++++++++++++++++++++---
 src/pdns-dhcp/Kea/KeaDhcp4LeaseHandler.cs |  5 +-
 src/pdns-dhcp/Kea/KeaDhcpLease.cs         | 49 +++++++++++++++
 src/pdns-dhcp/Kea/KeaDhcpLeaseWatcher.cs  |  8 ++-
 src/pdns-dhcp/pdns-dhcp.csproj            |  1 +
 5 files changed, 124 insertions(+), 11 deletions(-)
 create mode 100644 src/pdns-dhcp/Kea/KeaDhcpLease.cs

diff --git a/src/pdns-dhcp/Kea/KeaDhcp4Lease.cs b/src/pdns-dhcp/Kea/KeaDhcp4Lease.cs
index c5186f4..fe5c437 100644
--- a/src/pdns-dhcp/Kea/KeaDhcp4Lease.cs
+++ b/src/pdns-dhcp/Kea/KeaDhcp4Lease.cs
@@ -1,17 +1,71 @@
+using System.Net;
+using System.Net.NetworkInformation;
+
+using nietras.SeparatedValues;
+
 namespace pdns_dhcp.Kea;
 
 // ref: https://github.com/isc-projects/kea/blob/Kea-2.5.3/src/lib/dhcpsrv/csv_lease_file4.h
 public record struct KeaDhcp4Lease(
-	string Address,
-	string HWAddr,
+	IPAddress Address,
+	PhysicalAddress HWAddr,
 	string? ClientId,
 	uint ValidLifetime,
-	ulong Expire,
-	string SubnetId,
-	byte FqdnFwd,
-	byte FqdnRev,
+	DateTimeOffset Expire,
+	uint SubnetId,
+	bool FqdnFwd,
+	bool FqdnRev,
 	string Hostname,
 	uint State,
-	string UserContext,
-	uint PoolId
-);
+	string? UserContext,
+	uint PoolId)
+{
+	public static KeaDhcp4Lease Parse(in SepReader.Row row)
+	{
+		var address = IPAddress.Parse(row[0].Span);
+		PhysicalAddress hwaddr = PhysicalAddress.None;
+		if (row[1].Span is { IsEmpty: false } physical)
+		{
+			hwaddr = PhysicalAddress.Parse(physical);
+		}
+		string? clientId = row[2].ToString();
+		uint validLifetime = uint.Parse(row[3].Span);
+		DateTimeOffset expire = DateTimeOffset.FromUnixTimeSeconds(unchecked((long)ulong.Parse(row[4].Span)));
+		uint subnetId = uint.Parse(row[5].Span);
+		bool fqdnFwd = sbyte.Parse(row[6].Span) != 0;
+		bool fqdnRev = sbyte.Parse(row[7].Span) != 0;
+		string hostname = KeaDhcpLease.Unescape(row[8].Span);
+
+		uint state = 0;
+		if (row.ColCount > 9)
+		{
+			state = uint.Parse(row[9].Span);
+		}
+
+		string? userContext = default;
+		if (row.ColCount > 10)
+		{
+			userContext = KeaDhcpLease.Unescape(row[10].Span);
+		}
+
+		uint poolId = 0;
+		if (row.ColCount > 11)
+		{
+			poolId = uint.Parse(row[11].Span);
+		}
+
+		return new(
+			address,
+			hwaddr,
+			clientId,
+			validLifetime,
+			expire,
+			subnetId,
+			fqdnFwd,
+			fqdnRev,
+			hostname,
+			state,
+			userContext,
+			poolId);
+	}
+}
diff --git a/src/pdns-dhcp/Kea/KeaDhcp4LeaseHandler.cs b/src/pdns-dhcp/Kea/KeaDhcp4LeaseHandler.cs
index 202a3f4..5af3533 100644
--- a/src/pdns-dhcp/Kea/KeaDhcp4LeaseHandler.cs
+++ b/src/pdns-dhcp/Kea/KeaDhcp4LeaseHandler.cs
@@ -4,5 +4,8 @@ namespace pdns_dhcp.Kea;
 
 public class KeaDhcp4LeaseHandler : IKeaDhcpLeaseHandler
 {
-	public void Handle(in SepReader.Row row) { }
+	public void Handle(in SepReader.Row row)
+	{
+		KeaDhcp4Lease lease = KeaDhcp4Lease.Parse(row);
+	}
 }
diff --git a/src/pdns-dhcp/Kea/KeaDhcpLease.cs b/src/pdns-dhcp/Kea/KeaDhcpLease.cs
new file mode 100644
index 0000000..ae24491
--- /dev/null
+++ b/src/pdns-dhcp/Kea/KeaDhcpLease.cs
@@ -0,0 +1,49 @@
+using System.Buffers;
+using System.Globalization;
+
+using DotNext.Buffers;
+
+namespace pdns_dhcp.Kea;
+
+public static class KeaDhcpLease
+{
+	private static ReadOnlySpan<char> EscapeTag => ['&', '#', 'x'];
+
+	public static string Unescape(in ReadOnlySpan<char> text)
+	{
+		int esc_pos = text.IndexOf(EscapeTag);
+		return esc_pos == -1 ? text.ToString() : SlowPath(esc_pos, text);
+
+		static string SlowPath(int esc_pos, in ReadOnlySpan<char> text)
+		{
+			SpanReader<char> reader = new(text);
+			ArrayBufferWriter<char> writer = new(text.Length);
+			while (reader.RemainingCount > 0)
+			{
+				writer.Write(reader.Read(esc_pos));
+				reader.Advance(EscapeTag.Length);
+				if (EscapeTag.Length <= reader.RemainingCount - 2)
+				{
+					var digits = reader.Read(2);
+					if (byte.TryParse(digits, NumberStyles.AllowHexSpecifier, null, out var escaped_char))
+					{
+						writer.Write((char)escaped_char);
+					}
+					else
+					{
+						writer.Write(EscapeTag);
+						writer.Write(digits);
+					}
+				}
+
+				esc_pos = reader.RemainingSpan.IndexOf(EscapeTag);
+				if (esc_pos == -1)
+				{
+					writer.Write(reader.ReadToEnd());
+				}
+			}
+
+			return writer.WrittenSpan.ToString();
+		}
+	}
+}
diff --git a/src/pdns-dhcp/Kea/KeaDhcpLeaseWatcher.cs b/src/pdns-dhcp/Kea/KeaDhcpLeaseWatcher.cs
index 116abcc..d13091c 100644
--- a/src/pdns-dhcp/Kea/KeaDhcpLeaseWatcher.cs
+++ b/src/pdns-dhcp/Kea/KeaDhcpLeaseWatcher.cs
@@ -163,7 +163,11 @@ public sealed class KeaDhcpLeaseWatcher<T> : IHostedService
 				{
 					if (reader is null)
 					{
-						reader = Sep.Reader().From(_pipe.Reader.AsStream());
+						reader = Sep.New(',').Reader(o => o with
+						{
+							DisableColCountCheck = true,
+							Unescape = false
+						}).From(_pipe.Reader.AsStream());
 						continue;
 					}
 
@@ -172,6 +176,8 @@ public sealed class KeaDhcpLeaseWatcher<T> : IHostedService
 						// TODO Error state.
 						return;
 					}
+
+					_handler.Handle(reader.Current);
 				}
 
 				var memory = writer.GetMemory();
diff --git a/src/pdns-dhcp/pdns-dhcp.csproj b/src/pdns-dhcp/pdns-dhcp.csproj
index 38c7c18..3130929 100644
--- a/src/pdns-dhcp/pdns-dhcp.csproj
+++ b/src/pdns-dhcp/pdns-dhcp.csproj
@@ -10,6 +10,7 @@
 	</PropertyGroup>
 
 	<ItemGroup>
+		<PackageReference Include="DotNext" Version="4.15.2" />
 		<PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="8.0.0" />
 		<PackageReference Include="Microsoft.Extensions.Hosting" Version="8.0.0" />
 		<PackageReference Include="Sep" Version="0.3.0" />