ipv4: checksumming and processing

kernel-src/io/net/eth.c

@@ -15,12 +15,11 @@ void eth_process(netdev_t *netdev, void *buffer) {
 	if (!(MAC_EQUAL(&dst, &netdev->mac) || MAC_EQUAL(&dst, &broadcast)))
 		return;
 
-	printf("our machine!\n");
-
 	void *nextbuff = (void *)((uintptr_t)buffer + sizeof(ethframe_t));
 
 	switch (be_to_cpu_w(frame->type)) {
 		case ETH_PROTO_IP:
+			ipv4_process(netdev, nextbuff);
 			break;
 		case ETH_PROTO_ARP:
 			arp_process(netdev, nextbuff);

kernel-src/io/net/ipv4.c

@@ -4,6 +4,7 @@
 #include <logging.h>
 #include <mutex.h>
 #include <kernel/alloc.h>
+#include <kernel/abi.h>
 
 typedef struct {
 	netdev_t *netdev;
@@ -79,6 +80,27 @@ int ipv4_addroute(netdev_t *netdev, uint32_t addr, uint32_t gateway, uint32_t ma
 #define FLAG_MF 1
 // offset has to be a multiple of 8
 #define FLAGS_FRAGOFFSET(flg, offset) (((flg) << 13) | ((offset) >> 3))
+#define GET_FLAGS(x) (((x) >> 13) & 0x7)
+#define GET_FRAGOFFSET(x) ((x) & 0x1fff)
+
+static int checksum(void *buffer, size_t size) {
+	uint16_t *p = buffer;
+	int sum = 0;
+	int i;
+	for (int i = 0; i < (size & ~(1lu)); i += 2) {
+		sum += be_to_cpu_w(p[i >> 1]);
+	}
+
+	if (size & 1) {
+		sum += ((uint8_t *)p)[i];
+	}
+
+	sum = (sum >> 16) + (sum & 0xffff);
+	sum += sum >> 16;
+
+	uint16_t ret = ~sum;
+	return ret;
+}
 
 static int dispatch_fragment(netdev_t *netdev, netdesc_t fragdesc, 
 	uintmax_t fragmentoffset, size_t fragmentlen, int id, uint32_t ip, mac_t mac, int proto, bool last) {
@@ -90,15 +112,50 @@ static int dispatch_fragment(netdev_t *netdev, netdesc_t fragdesc,
 		.flags_fragoffset = cpu_to_be_w(FLAGS_FRAGOFFSET(!last ? FLAG_MF : 0, fragmentoffset)),
 		.timetolive = 0xff,
 		.protocol = proto,
-		.framechecksum = 0xfefe, // TODO checksum
+		.framechecksum = 0,
-		.srcaddr = netdev->ip, // TODO src addr
+		.srcaddr = cpu_to_be_d(netdev->ip),
 		.dstaddr = cpu_to_be_d(ip)
 	};
 
+	frame.framechecksum = cpu_to_be_w(checksum(&frame, sizeof(frame)));
+
 	memcpy((void *)((uintptr_t)fragdesc.address + fragdesc.curroffset), &frame, sizeof(ipv4frame_t));
 	return netdev->sendpacket(netdev, fragdesc, mac, ETH_PROTO_IP);
 }
 
+void ipv4_process(netdev_t *netdev, void *buff) {
+	ipv4frame_t *frame = buff;
+
+	if (checksum(frame, sizeof(ipv4frame_t)) != 0) {
+		return;
+	}
+
+	if (frame->version_length != VERSION_LENGTH(4, 5))
+		return;
+
+	uint16_t flagsfrag = be_to_cpu_w(frame->flags_fragoffset);
+	if ((GET_FLAGS(flagsfrag) & FLAG_MF) || (GET_FRAGOFFSET(flagsfrag) > 0)) {
+		printf("ipv4: reassembly not yet supported\n");
+		return;
+	}
+
+	uint32_t dstip = be_to_cpu_d(frame->dstaddr);
+	uint32_t srcip = be_to_cpu_d(frame->srcaddr);
+
+	if (dstip != IPV4_BROADCAST_ADDRESS && dstip != netdev->ip)
+		return;
+
+	void *nextbuff = (void *)((uintptr_t)buff + sizeof(ipv4frame_t));
+
+	switch (frame->protocol) {
+		case IPV4_PROTO_UDP:
+			udp_process(netdev, nextbuff, srcip);
+			break;
+	}
+
+	return;
+}
+
 int ipv4_sendpacket(void *buffer, size_t packetsize, uint32_t ip, int proto, netdev_t *broadcastdev) {
 	if ((packetsize + sizeof(ipv4frame_t)) > 65535)
 		return EMSGSIZE;
@@ -134,7 +191,8 @@ int ipv4_sendpacket(void *buffer, size_t packetsize, uint32_t ip, int proto, net
 		if (e)
 			return e;
 
-		memcpy((void *)((uintptr_t)fragdesc.address + sizeof(ipv4frame_t)), (void *)((uintptr_t)buffer + i * devfragmentsize), fragmentlen);
+		memcpy((void *)((uintptr_t)fragdesc.address + fragdesc.curroffset + sizeof(ipv4frame_t)), (void *)((uintptr_t)buffer + i * devfragmentsize), fragmentlen);
+
 		e = dispatch_fragment(netdev, fragdesc, i * devfragmentsize, fragmentlen, 0x1234, ip, mac, proto, i == fragmentcount - 1);
 		// TODO unallocate desc
 		if (e)