From 1be8b626d2de6f4f586aae191eba9544262a1f8c Mon Sep 17 00:00:00 2001
From: sdomi <ja@sdomi.pl>
Date: Tue, 10 Sep 2024 23:49:30 +0200
Subject: [PATCH] Kernel/Net: Introduce proper pointers for payload calls

Unifying with other structures, this introduces m_payload for all
relevant structures, except the TCP header (which has a different
concept of payload than the rest).

This allows us to return a pointer directly instead of doing pointer
arithmetic to point to the end of the structure.
---
 Kernel/Net/EthernetFrameHeader.h |  2 +-
 Kernel/Net/ICMP.h                | 12 +++++++-----
 Kernel/Net/IP/IPv4.h             |  5 +++--
 Kernel/Net/UDP.h                 |  5 +++--
 4 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/Kernel/Net/EthernetFrameHeader.h b/Kernel/Net/EthernetFrameHeader.h
index 8468d0b588d11f..c1cb75dc34dc9b 100644
--- a/Kernel/Net/EthernetFrameHeader.h
+++ b/Kernel/Net/EthernetFrameHeader.h
@@ -32,7 +32,7 @@ class [[gnu::packed]] EthernetFrameHeader {
     MACAddress m_destination;
     MACAddress m_source;
     NetworkOrdered<u16> m_ether_type;
-    u32 m_payload[0];
+    u8 m_payload[0];
 };
 
 static_assert(sizeof(EthernetFrameHeader) == 14);
diff --git a/Kernel/Net/ICMP.h b/Kernel/Net/ICMP.h
index 99656db7e319d0..b7f3fd0aa2debf 100644
--- a/Kernel/Net/ICMP.h
+++ b/Kernel/Net/ICMP.h
@@ -30,14 +30,14 @@ class [[gnu::packed]] ICMPHeader {
     u16 checksum() const { return m_checksum; }
     void set_checksum(u16 w) { m_checksum = w; }
 
-    void const* payload() const { return this + 1; }
-    void* payload() { return this + 1; }
+    void const* payload() const { return &m_payload[0]; }
+    void* payload() { return &m_payload[0]; }
 
 private:
     u8 m_type { 0 };
     u8 m_code { 0 };
     NetworkOrdered<u16> m_checksum { 0 };
-    // NOTE: The rest of the header is 4 bytes
+    u8 m_payload[0];
 };
 
 static_assert(AssertSize<ICMPHeader, 4>());
@@ -46,6 +46,8 @@ struct [[gnu::packed]] ICMPEchoPacket {
     ICMPHeader header;
     NetworkOrdered<u16> identifier;
     NetworkOrdered<u16> sequence_number;
-    void* payload() { return this + 1; }
-    void const* payload() const { return this + 1; }
+    u8 m_payload[0];
+
+    void* payload() { return &m_payload[0]; }
+    void const* payload() const { return &m_payload[0]; }
 };
diff --git a/Kernel/Net/IP/IPv4.h b/Kernel/Net/IP/IPv4.h
index 62977e6b788e84..0daee35ccdae4d 100644
--- a/Kernel/Net/IP/IPv4.h
+++ b/Kernel/Net/IP/IPv4.h
@@ -51,8 +51,8 @@ class [[gnu::packed]] IPv4Packet {
     IPv4Address const& destination() const { return m_destination; }
     void set_destination(IPv4Address const& address) { m_destination = address; }
 
-    void* payload() { return this + 1; }
-    void const* payload() const { return this + 1; }
+    void* payload() { return &m_payload[0]; }
+    void const* payload() const { return &m_payload[0]; }
 
     u16 flags_and_fragment() const { return m_flags_and_fragment; }
     u16 fragment_offset() const { return ((u16)m_flags_and_fragment & 0x1fff); }
@@ -97,6 +97,7 @@ class [[gnu::packed]] IPv4Packet {
     NetworkOrdered<u16> m_checksum;
     IPv4Address m_source;
     IPv4Address m_destination;
+    u8 m_payload[0];
 };
 
 static_assert(AssertSize<IPv4Packet, 20>());
diff --git a/Kernel/Net/UDP.h b/Kernel/Net/UDP.h
index bcbc6e8cbef506..23f691bccc4e01 100644
--- a/Kernel/Net/UDP.h
+++ b/Kernel/Net/UDP.h
@@ -27,14 +27,15 @@ class [[gnu::packed]] UDPPacket {
     u16 checksum() const { return m_checksum; }
     void set_checksum(u16 checksum) { m_checksum = checksum; }
 
-    void const* payload() const { return this + 1; }
-    void* payload() { return this + 1; }
+    void const* payload() const { return &m_payload[0]; }
+    void* payload() { return &m_payload[0]; }
 
 private:
     NetworkOrdered<u16> m_source_port;
     NetworkOrdered<u16> m_destination_port;
     NetworkOrdered<u16> m_length;
     NetworkOrdered<u16> m_checksum;
+    u8 m_payload[0];
 };
 
 static_assert(sizeof(UDPPacket) == 8);