From f804e87f7deb8c4bd80603f77969459c97e8a8b2 Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Mon, 5 Feb 2024 17:38:57 +0200
Subject: [PATCH] Kernel: Implement basic gateway for network interfaces

---
 .../kernel/Networking/NetworkInterface.h      |  4 ++++
 kernel/kernel/Networking/ARPTable.cpp         |  3 +++
 kernel/kernel/Networking/NetworkSocket.cpp    | 16 ++++++++++++++
 libc/include/net/if.h                         |  5 ++++-
 userspace/dhcp-client/main.cpp                | 21 +++++++++++++++++--
 5 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/kernel/include/kernel/Networking/NetworkInterface.h b/kernel/include/kernel/Networking/NetworkInterface.h
index b23c3c1402..50ff40fdc3 100644
--- a/kernel/include/kernel/Networking/NetworkInterface.h
+++ b/kernel/include/kernel/Networking/NetworkInterface.h
@@ -46,6 +46,9 @@ namespace Kernel
 		BAN::IPv4Address get_netmask() const { return m_netmask; }
 		void set_netmask(BAN::IPv4Address new_netmask) { m_netmask = new_netmask; }
 
+		BAN::IPv4Address get_gateway() const { return m_gateway; }
+		void set_gateway(BAN::IPv4Address new_gateway) { m_gateway = new_gateway; }
+
 		virtual bool link_up() = 0;
 		virtual int link_speed() = 0;
 
@@ -65,6 +68,7 @@ namespace Kernel
 
 		BAN::IPv4Address m_ipv4_address { 0 };
 		BAN::IPv4Address m_netmask { 0 };
+		BAN::IPv4Address m_gateway { 0 };
 	};
 
 }
diff --git a/kernel/kernel/Networking/ARPTable.cpp b/kernel/kernel/Networking/ARPTable.cpp
index b9f23842e7..ba98a5a3e3 100644
--- a/kernel/kernel/Networking/ARPTable.cpp
+++ b/kernel/kernel/Networking/ARPTable.cpp
@@ -45,6 +45,9 @@ namespace Kernel
 		if (ipv4_address == s_broadcast_ipv4)
 			return s_broadcast_mac;
 
+		if (interface.get_ipv4_address().mask(interface.get_netmask()) != ipv4_address.mask(interface.get_netmask()))
+			ipv4_address = interface.get_gateway();
+
 		{
 			LockGuard _(m_lock);
 			if (m_arp_table.contains(ipv4_address))
diff --git a/kernel/kernel/Networking/NetworkSocket.cpp b/kernel/kernel/Networking/NetworkSocket.cpp
index 5c5618bd7b..e0943e0f51 100644
--- a/kernel/kernel/Networking/NetworkSocket.cpp
+++ b/kernel/kernel/Networking/NetworkSocket.cpp
@@ -171,6 +171,22 @@ namespace Kernel
 				dprintln("Netmask set to {}", m_interface->get_netmask());
 				return 0;
 			}
+			case SIOCGIFGWADDR:
+			{
+				auto& ifru_gwaddr = *reinterpret_cast<sockaddr_in*>(&ifreq->ifr_ifru.ifru_gwaddr);
+				ifru_gwaddr.sin_family = AF_INET;
+				ifru_gwaddr.sin_addr.s_addr = m_interface->get_gateway().raw;
+				return 0;
+			}
+			case SIOCSIFGWADDR:
+			{
+				auto& ifru_gwaddr = *reinterpret_cast<const sockaddr_in*>(&ifreq->ifr_ifru.ifru_gwaddr);
+				if (ifru_gwaddr.sin_family != AF_INET)
+					return BAN::Error::from_errno(EADDRNOTAVAIL);
+				m_interface->set_gateway(BAN::IPv4Address { ifru_gwaddr.sin_addr.s_addr });
+				dprintln("Gateway set to {}", m_interface->get_gateway());
+				return 0;
+			}
 			case SIOCGIFHWADDR:
 			{
 				auto mac_address = m_interface->get_mac_address();
diff --git a/libc/include/net/if.h b/libc/include/net/if.h
index 89600f4600..39de6da224 100644
--- a/libc/include/net/if.h
+++ b/libc/include/net/if.h
@@ -22,6 +22,7 @@ struct ifreq
 	union {
 		struct sockaddr ifru_addr;
 		struct sockaddr ifru_netmask;
+		struct sockaddr ifru_gwaddr;
 		struct sockaddr ifru_hwaddr;
 		unsigned char __min_storage[sizeof(sockaddr) + 6];
 	} ifr_ifru;
@@ -31,7 +32,9 @@ struct ifreq
 #define SIOCSIFADDR		2	/* Set interface address */
 #define SIOCGIFNETMASK	3	/* Get network mask */
 #define SIOCSIFNETMASK	4	/* Set network mask */
-#define SIOCGIFHWADDR	5	/* Get hardware address */
+#define SIOCGIFGWADDR	5	/* Get gateway address */
+#define SIOCSIFGWADDR	6	/* Set gateway address */
+#define SIOCGIFHWADDR	7	/* Get hardware address */
 
 void					if_freenameindex(struct if_nameindex* ptr);
 char*					if_indextoname(unsigned ifindex, char* ifname);
diff --git a/userspace/dhcp-client/main.cpp b/userspace/dhcp-client/main.cpp
index 88a522029e..3e01cd90d9 100644
--- a/userspace/dhcp-client/main.cpp
+++ b/userspace/dhcp-client/main.cpp
@@ -73,7 +73,7 @@ BAN::MACAddress get_mac_address(int socket)
 	return mac_address;
 }
 
-void update_ipv4_info(int socket, BAN::IPv4Address address, BAN::IPv4Address subnet)
+void update_ipv4_info(int socket, BAN::IPv4Address address, BAN::IPv4Address netmask, BAN::IPv4Address gateway)
 {
 	{
 		ifreq ifreq;
@@ -98,6 +98,19 @@ void update_ipv4_info(int socket, BAN::IPv4Address address, BAN::IPv4Address sub
 			exit(1);
 		}
 	}
+
+	if (gateway.raw)
+	{
+		ifreq ifreq;
+		auto& ifru_gwaddr = *reinterpret_cast<sockaddr_in*>(&ifreq.ifr_ifru.ifru_gwaddr);
+		ifru_gwaddr.sin_family = AF_INET;
+		ifru_gwaddr.sin_addr.s_addr = gateway.raw;
+		if (ioctl(socket, SIOCSIFGWADDR, &ifreq) == -1)
+		{
+			perror("ioctl");
+			exit(1);
+		}
+	}
 }
 
 void send_dhcp_packet(int socket, const DHCPPacket& dhcp_packet, BAN::IPv4Address server_ipv4)
@@ -359,7 +372,11 @@ int main()
 		return 1;
 	}
 
-	update_ipv4_info(socket, dhcp_ack->address, dhcp_ack->subnet);
+	BAN::IPv4Address gateway { 0 };
+	if (!dhcp_ack->routers.empty())
+		gateway = dhcp_ack->routers.front();
+
+	update_ipv4_info(socket, dhcp_ack->address, dhcp_ack->subnet, gateway);
 
 	close(socket);