From f4d5425c185b76509e5f98bec5b6394eb250e73c Mon Sep 17 00:00:00 2001
From: Matheus <matheusuky@gmail.com>
Date: Fri, 29 Mar 2024 13:40:55 -0300
Subject: [PATCH] ipv4: initial tx only implementation

---
 kernel-src/io/net/ipv4.c | 56 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 kernel-src/io/net/ipv4.c

diff --git a/kernel-src/io/net/ipv4.c b/kernel-src/io/net/ipv4.c
new file mode 100644
index 00000000..bcf378d8
--- /dev/null
+++ b/kernel-src/io/net/ipv4.c
@@ -0,0 +1,56 @@
+#include <kernel/net.h>
+#include <arch/cpu.h>
+#include <logging.h>
+
+int ipv4_allocdesc(netdev_t *netdev, size_t requestedsize, netdesc_t *desc) {
+	int e = netdev->allocdesc(requestedsize + sizeof(ipv4frame_t), desc);
+	desc->curroffset += sizeof(ipv4frame_t);
+	return e;
+}
+
+#define VERSION_LENGTH(v, l) (((v) << 4) | l)
+
+#define FLAG_MF 1
+// offset has to be a multiple of 8
+#define FLAGS_FRAGOFFSET(flg, offset) (((flg) << 13) | ((offset) >> 3))
+
+static int dispatch_fragment(netdev_t *netdev, netdesc_t originaldesc, netdesc_t fragdesc, 
+	uintmax_t fragmentoffset, size_t fragmentlen, int id, uint32_t ip, int proto) {
+	ipv4frame_t frame = {
+		.version_length = VERSION_LENGTH(4, 5),
+		.servicetype_ecn = 0,
+		.packetlen = cpu_to_be_w(fragmentlen + sizeof(ipv4frame_t)),
+		.id = cpu_to_be_w(0x1234), // TODO proper id allocation per netdev
+		.flags_fragoffset = cpu_to_be_w(FLAGS_FRAGOFFSET((fragmentoffset + fragmentlen < originaldesc.size - originaldesc.curroffset - sizeof(ipv4frame_t)) ? FLAG_MF : 0, fragmentoffset)),
+		.timetolive = 0xff,
+		.protocol = proto,
+		.framechecksum = 0xfefe, // TODO checksum
+		.srcaddr = 0xffffffff, // TODO src addr
+		.dstaddr = cpu_to_be_d(ip)
+	};
+
+	memcpy((void *)((uintptr_t)fragdesc.address + fragdesc.curroffset), &frame, sizeof(ipv4frame_t));
+	memcpy((void *)((uintptr_t)fragdesc.address + fragdesc.curroffset + sizeof(ipv4frame_t)), originaldesc.address + originaldesc.curroffset + sizeof(ipv4frame_t) + fragmentoffset, fragmentlen);
+	return netdev->sendpacket(netdev, fragdesc, NET_BROADCAST_MAC, ETH_PROTO_IP);
+}
+
+int ipv4_sendpacket(netdev_t *netdev, netdesc_t desc, uint32_t ip, int proto) {
+	size_t datasize = desc.size - desc.curroffset;
+	desc.curroffset -= sizeof(ipv4frame_t);
+	__assert(desc.size - desc.curroffset <= 65535);
+	
+	size_t mtuheader = netdev->mtu - sizeof(ipv4frame_t);
+	size_t devfragmentsize = mtuheader - (mtuheader % 8);
+	size_t fragmentcount = datasize / devfragmentsize + 1;
+
+	for (int i = 0; i < fragmentcount; ++i) {
+		size_t fragmentlen = (i == fragmentcount - 1) ? datasize - devfragmentsize * (fragmentcount - 1) : devfragmentsize;
+		netdesc_t fragdesc;
+		__assert(ipv4_allocdesc(netdev, fragmentlen + sizeof(ipv4frame_t), &fragdesc) == 0);
+		fragdesc.curroffset -= sizeof(ipv4frame_t);
+		dispatch_fragment(netdev, desc, fragdesc, i * devfragmentsize, fragmentlen, 0x1234, ip, proto);
+		// TODO unallocate desc
+	}
+
+	return 0; // TODO error handling
+}