1 files changed, 83 insertions, 0 deletions
diff --git a/network/arp.c b/network/arp.c
new file mode 100644
index 0000000..eb8aca3
--- /dev/null
+++ b/network/arp.c
@@ -0,0 +1,83 @@
+#include <assert.h>
+#include <drivers/rtl8139.h>
+#include <network/arp.h>
+#include <network/bytes.h>
+#include <network/ethernet.h>
+#include <stdio.h>
+#include <string.h>
+
+struct ARP_DATA {
+  uint16_t htype;   // Hardware type
+  uint16_t ptype;   // Protocol type
+  uint8_t hlen;     // Hardware address length (Ethernet = 6)
+  uint8_t plen;     // Protocol address length (IPv4 = 4)
+  uint16_t opcode;  // ARP Operation Code
+  uint8_t srchw[6]; // Source hardware address - hlen bytes (see above)
+  uint8_t srcpr[4]; // Source protocol address - plen bytes (see above).
+                    // If IPv4 can just be a "u32" type.
+  uint8_t dsthw[6]; // Destination hardware address - hlen bytes (see above)
+  uint8_t dstpr[4]; // Destination protocol address - plen bytes (see
+                    // above). If IPv4 can just be a "u32" type.
+};
+
+// FIXME: This is hardcoded, don't do this.
+uint8_t ip_address[4] = {10, 0, 2, 15};
+
+void print_mac(const char *str, uint8_t *mac) {
+  kprintf("%s: ", str);
+  for (int i = 0; i < 6; i++) {
+    kprintf("%x", mac[i]);
+    if (5 != i)
+      kprintf(":");
+  }
+  kprintf("\n");
+}
+
+void print_ip(const char *str, uint8_t *ip) {
+  kprintf("%s: ", str);
+  for (int i = 0; i < 4; i++) {
+    kprintf("%d", ip[i]);
+    if (3 != i)
+      kprintf(".");
+  }
+  kprintf("\n");
+}
+
+void handle_arp(uint8_t *payload) {
+  struct ARP_DATA *data = (struct ARP_DATA *)payload;
+
+  // Assert that communication is over ethernet
+  assert(1 == ntohs(data->htype));
+  // Assert it is a request
+  assert(0x0001 == ntohs(data->opcode));
+  // Assert that request uses IP
+  assert(0x0800 == ntohs(data->ptype));
+
+  assert(6 == data->hlen);
+  assert(4 == data->plen);
+  print_mac("srchw: ", data->srchw);
+  print_ip("srcpr: ", data->srcpr);
+
+  print_mac("dsthw: ", data->dsthw);
+  print_ip("dstpr: ", data->dstpr);
+
+  uint8_t mac[6];
+  get_mac_address(mac);
+  print_mac("THIS DEVICE MAC: ", mac);
+  assert(0 == memcmp(data->dstpr, ip_address, sizeof(uint8_t[4])));
+
+  // Now we have to construct a ARP response
+  struct ARP_DATA response;
+  response.htype = htons(1);
+  response.ptype = htons(0x0800);
+  response.opcode = htons(0x00002);
+  response.hlen = 6;
+  response.plen = 4;
+  get_mac_address(response.srchw);
+  memcpy(response.srcpr, ip_address, sizeof(uint8_t[4]));
+
+  memcpy(response.dsthw, data->srchw, sizeof(uint8_t[6]));
+  memcpy(response.dstpr, data->srcpr, sizeof(uint8_t[4]));
+
+  send_ethernet_packet(data->srchw, 0x0806, (uint8_t*)&response, sizeof(response));
+}