user: rename ethdump to netstack

1 files changed, 48 insertions, 0 deletions

diff --git a/src/user/app/netstack/arp.c b/src/user/app/netstack/arp.c
new file mode 100644
index 0000000..cfb1e04
--- /dev/null
+++ b/src/user/app/netstack/arp.c
@@ -0,0 +1,48 @@
+#include "proto.h"
+#include "util.h"
+#include <string.h>
+
+enum {
+	HdrType   = 0,
+		HdrTypeEther = 1,
+	ProtoType = 2,
+	HdrALen   = 4,
+	ProtoALen = 5,
+	Operation = 6,
+		OpReq   = 1,
+		OpReply = 2,
+};
+
+void arp_parse(const uint8_t *buf, size_t len) {
+	// TODO no bound checks
+	uint16_t htype = nget16(buf + HdrType);
+	uint16_t ptype = nget16(buf + ProtoType);
+	uint16_t op = nget16(buf + Operation);
+
+	if (!(htype == HdrTypeEther && ptype == ET_IPv4)) return;
+	enum { /* only valid for this combination of header + proto */
+		SrcMAC =  8,
+		SrcIP  = 14,
+		DstMAC = 18,
+		DstIP  = 24,
+	};
+
+	if (op == OpReq) {
+		uint32_t daddr = nget32(buf + DstIP);
+		if (daddr == state.ip) {
+			uint8_t *pkt = ether_start(30, (struct ethernet){
+				.dst = buf + SrcMAC,
+				.type = ET_ARP,
+			});
+			nput16(pkt + HdrType, 1);
+			nput16(pkt + ProtoType, ET_IPv4);
+			pkt[HdrALen] = 6;
+			pkt[ProtoALen] = 4;
+			nput16(pkt + Operation, OpReply);
+			memcpy(pkt + SrcMAC, state.mac, 6);
+			nput32(pkt + SrcIP, state.ip);
+			memcpy(pkt + DstMAC, buf + SrcMAC, 10); /* sender's MAC and IP */
+			ether_finish(pkt);
+		}
+	}
+}