From 3440dbb1fc0b13eb81d25f26ed54f7df4508a459 Mon Sep 17 00:00:00 2001
From: AnotherTest <ali.mpfard@gmail.com>
Date: Mon, 15 Feb 2021 21:36:57 +0330
Subject: [PATCH] DHCPClient: Don't reject packets smaller than the max size

It's acceptable to have less padding in a packet, the only requirement
is to have a single byte of 'END' in the DHCP fields.
---
 Userland/Services/DHCPClient/DHCPv4Client.cpp | 6 ++++--
 Userland/Services/DHCPClient/main.cpp         | 6 ++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/Userland/Services/DHCPClient/DHCPv4Client.cpp b/Userland/Services/DHCPClient/DHCPv4Client.cpp
index ecb76f107d..945b2b54a4 100644
--- a/Userland/Services/DHCPClient/DHCPv4Client.cpp
+++ b/Userland/Services/DHCPClient/DHCPv4Client.cpp
@@ -53,7 +53,9 @@ static void send(const InterfaceDescriptor& iface, const DHCPv4Packet& packet, C
     dst.sin_addr.s_addr = IPv4Address { 255, 255, 255, 255 }.to_u32();
     memset(&dst.sin_zero, 0, sizeof(dst.sin_zero));
 
+    dbgln_if(DHCPV4CLIENT_DEBUG, "sendto({} bound to {}, ..., {} at {}) = ...?", fd, iface.m_ifname, dst.sin_addr.s_addr, dst.sin_port);
     auto rc = sendto(fd, &packet, sizeof(packet), 0, (sockaddr*)&dst, sizeof(dst));
+    dbgln_if(DHCPV4CLIENT_DEBUG, "sendto({}) = {}", fd, rc);
     if (rc < 0) {
         dbgln("sendto failed with {}", strerror(errno));
         // FIXME: what do we do here?
@@ -113,8 +115,8 @@ DHCPv4Client::DHCPv4Client(Vector<InterfaceDescriptor> ifnames)
     m_server->on_ready_to_receive = [this] {
         auto buffer = m_server->receive(sizeof(DHCPv4Packet));
         dbgln("Received {} bytes", buffer.size());
-        if (buffer.size() != sizeof(DHCPv4Packet)) {
-            dbgln("we expected {} bytes, this is a bad packet", sizeof(DHCPv4Packet));
+        if (buffer.size() < sizeof(DHCPv4Packet) - DHCPV4_OPTION_FIELD_MAX_LENGTH + 1 || buffer.size() > sizeof(DHCPv4Packet)) {
+            dbgln("we expected {}-{} bytes, this is a bad packet", sizeof(DHCPv4Packet) - DHCPV4_OPTION_FIELD_MAX_LENGTH + 1, sizeof(DHCPv4Packet));
             return;
         }
         auto& packet = *(DHCPv4Packet*)buffer.data();
diff --git a/Userland/Services/DHCPClient/main.cpp b/Userland/Services/DHCPClient/main.cpp
index 62f51f3fbc..9e77dfb816 100644
--- a/Userland/Services/DHCPClient/main.cpp
+++ b/Userland/Services/DHCPClient/main.cpp
@@ -25,6 +25,7 @@
  */
 
 #include "DHCPv4Client.h"
+#include <AK/Debug.h>
 #include <AK/JsonArray.h>
 #include <AK/JsonObject.h>
 #include <AK/String.h>
@@ -69,7 +70,7 @@ int main([[maybe_unused]] int argc, [[maybe_unused]] char** argv)
 
     auto file = Core::File::construct("/proc/net/adapters");
     if (!file->open(Core::IODevice::ReadOnly)) {
-        warnln("Error: {}", file->error_string());
+        dbgln("Error: {}", file->error_string());
         return 1;
     }
 
@@ -77,7 +78,7 @@ int main([[maybe_unused]] int argc, [[maybe_unused]] char** argv)
     auto json = JsonValue::from_string(file_contents);
 
     if (!json.has_value() || !json.value().is_array()) {
-        warnln("Error: No network adapters available");
+        dbgln("Error: No network adapters available");
         return 1;
     }
 
@@ -90,6 +91,7 @@ int main([[maybe_unused]] int argc, [[maybe_unused]] char** argv)
 
         auto name = if_object.get("name").to_string();
         auto mac = if_object.get("mac_address").to_string();
+        dbgln_if(DHCPV4_DEBUG, "Found adapter '{}' with mac {}", name, mac);
         ifnames.append({ name, mac_from_string(mac) });
     });