Kernel/LibC/Networking: Be able to send UDP messages

Now it can send UDP messages to a specific IP address and libc has
enough to create a basic UDP ECHO server, that is kinda cool.

7 files changed, 188 insertions, 40 deletions

diff --git a/network/arp.c b/network/arp.c
index f86c732..de6d898 100644
--- a/network/arp.c
+++ b/network/arp.c
@@ -20,9 +20,28 @@ struct ARP_DATA {
                     // above). If IPv4 can just be a "u32" type.
 };
 
+struct ARP_TABLE_ENTRY {
+  uint8_t is_used;
+  uint8_t mac[6];
+  uint8_t ip[4];
+};
+
+struct ARP_TABLE_ENTRY arp_table[10] = {0};
+
 // FIXME: This is hardcoded, don't do this.
 uint8_t ip_address[4] = {10, 0, 2, 15};
 
+struct ARP_TABLE_ENTRY *find_arp_entry_to_use(void) {
+  // This does not need to find a "free" entry as a ARP table is
+  // just a cache, it just has to pick a entry efficently.
+  for (int i = 0; i < 10; i++) {
+    if (!arp_table[i].is_used) {
+      return &arp_table[i];
+    }
+  }
+  return &arp_table[0];
+}
+
 void print_mac(const char *str, uint8_t *mac) {
   kprintf("%s: ", str);
   for (int i = 0; i < 6; i++) {
@@ -33,7 +52,7 @@ void print_mac(const char *str, uint8_t *mac) {
   kprintf("\n");
 }
 
-void print_ip(const char *str, uint8_t *ip) {
+void print_ip(const char *str, const uint8_t *ip) {
   kprintf("%s: ", str);
   for (int i = 0; i < 4; i++) {
     kprintf("%d", ip[i]);
@@ -43,42 +62,92 @@ void print_ip(const char *str, uint8_t *ip) {
   kprintf("\n");
 }
 
+void send_arp_request(const uint8_t ip[4]) {
+  struct ARP_DATA data;
+  data.htype = htons(1);
+  data.ptype = htons(0x0800);
+
+  data.hlen = 6;
+  data.plen = 4;
+
+  data.opcode = htons(0x0001);
+  get_mac_address(data.srchw);
+  memcpy(data.srcpr, ip_address, sizeof(uint8_t[4]));
+
+  memset(data.dsthw, 0, sizeof(uint8_t[6]));
+  memcpy(data.dstpr, ip, sizeof(uint8_t[4]));
+
+  uint8_t broadcast[6];
+  memset(broadcast, 0xFF, sizeof(broadcast));
+  send_ethernet_packet(broadcast, 0x0806, (uint8_t *)&data, sizeof(data));
+}
+
+int get_mac_from_ip(const uint8_t ip[4], uint8_t mac[6]) {
+  print_ip("ARP GETTING MAC FROM IP: ", ip);
+  for (int i = 0; i < 10; i++) {
+    if (0 != memcmp(arp_table[i].ip, ip, sizeof(uint8_t[4])))
+      continue;
+    memcpy(mac, arp_table[i].mac, sizeof(uint8_t[6]));
+    return 1;
+  }
+  klog("ARP cache miss", LOG_NOTE);
+  asm("sti");
+  send_arp_request(ip);
+  // TODO: Maybe wait a bit?
+  for (int i = 0; i < 10; i++) {
+    if (0 != memcmp(arp_table[i].ip, ip, sizeof(uint8_t[4])))
+      continue;
+    memcpy(mac, arp_table[i].mac, sizeof(uint8_t[6]));
+    return 1;
+  }
+  assert(0);
+  return 0;
+}
+
 void handle_arp(const 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);
+  // Assert it is a request
+  if (0x0001 /*arp_request*/ == ntohs(data->opcode)) {
+    print_mac("srchw: ", data->srchw);
+    print_ip("srcpr: ", data->srcpr);
 
-  print_mac("dsthw: ", data->dsthw);
-  print_ip("dstpr: ", data->dstpr);
+    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));
+    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));
+  } else if (0x0002 /*arp_response*/ == ntohs(data->opcode)) {
+    // Find a entry to fill
+    struct ARP_TABLE_ENTRY *entry = find_arp_entry_to_use();
+    entry->is_used = 1;
+    memcpy(entry->mac, data->srchw, sizeof(uint8_t[6]));
+    memcpy(entry->ip, data->srcpr, sizeof(uint8_t[4]));
+    print_ip("Added ip: ", entry->ip);
+  } else {
+    kprintf("GOT A ARP REQEUST WITH TYPE: %x\n", ntohs(data->opcode));
+    assert(0);
+  }
 }
diff --git a/network/arp.h b/network/arp.h
index 8efda97..c2beb94 100644
--- a/network/arp.h
+++ b/network/arp.h
@@ -1,3 +1,4 @@
 #include <stdint.h>
 
+int get_mac_from_ip(const uint8_t ip[4], uint8_t mac[6]);
 void handle_arp(const uint8_t *payload);
diff --git a/network/ethernet.c b/network/ethernet.c
index 11a3876..e97ccbd 100644
--- a/network/ethernet.c
+++ b/network/ethernet.c
@@ -55,17 +55,7 @@ void handle_ethernet(const uint8_t *packet, uint64_t packet_length) {
   kprintf("OUR OWN CALCULATED crc: %x\n",
           crc32((const char *)eth_header, (packet_length - 4)));
 
-  kprintf("mac dst: ");
-  for (int i = 0; i < 6; i++)
-    kprintf("%x", eth_header->mac_dst[i]);
-  kprintf("\n");
-  kprintf("mac src: ");
-  for (int i = 0; i < 6; i++)
-    kprintf("%x", eth_header->mac_src[i]);
-  kprintf("\n");
-
   uint16_t type = ntohs(eth_header->type);
-  kprintf("Etheretype: %x\n", type);
   switch (type) {
   case 0x0806:
     handle_arp(payload);
diff --git a/network/ipv4.c b/network/ipv4.c
index e7ef2c2..099aa0d 100644
--- a/network/ipv4.c
+++ b/network/ipv4.c
@@ -1,11 +1,78 @@
 #include <assert.h>
+#include <kmalloc.h>
+#include <network/arp.h>
 #include <network/bytes.h>
+#include <network/ethernet.h>
 #include <network/ipv4.h>
 #include <network/udp.h>
 #include <string.h>
 
+uint16_t ip_checksum(void *vdata, size_t length) {
+  // Cast the data pointer to one that can be indexed.
+  char *data = (char *)vdata;
+
+  // Initialise the accumulator.
+  uint32_t acc = 0xffff;
+
+  // Handle complete 16-bit blocks.
+  for (size_t i = 0; i + 1 < length; i += 2) {
+    uint16_t word;
+    memcpy(&word, data + i, 2);
+    acc += ntohs(word);
+    if (acc > 0xffff) {
+      acc -= 0xffff;
+    }
+  }
+
+  // Handle any partial block at the end of the data.
+  if (length & 1) {
+    uint16_t word = 0;
+    memcpy(&word, data + length - 1, 1);
+    acc += ntohs(word);
+    if (acc > 0xffff) {
+      acc -= 0xffff;
+    }
+  }
+
+  // Return the checksum in network byte order.
+  return htons(~acc);
+}
+
+extern uint8_t ip_address[4];
+void send_ipv4_packet(uint32_t ip, uint8_t protocol, const uint8_t *payload,
+                      uint16_t length) {
+  uint8_t header[20] = {0};
+  header[0] = (4 /*version*/ << 4) | (5 /*IHL*/);
+  *((uint16_t *)(header + 2)) = htons(length + 20);
+  header[8 /*TTL*/] = 0xF8;
+  header[9] = protocol;
+
+  memcpy(header + 12 /*src_ip*/, ip_address, sizeof(uint8_t[4]));
+  memcpy(header + 16, &ip, sizeof(uint8_t[4]));
+
+  *((uint16_t *)(header + 10 /*checksum*/)) = ip_checksum(header, 20);
+  uint16_t packet_length = length + 20;
+  uint8_t *packet = kmalloc(packet_length);
+  memcpy(packet, header, 20);
+  memcpy(packet + 20, payload, length);
+
+  uint8_t mac[6];
+  uint8_t ip_copy[4]; // TODO: Do I need to do this?
+  memcpy(ip_copy, &ip, sizeof(uint8_t[4]));
+  get_mac_from_ip(ip_copy, mac);
+  send_ethernet_packet(mac, 0x0800, packet, packet_length);
+  kfree(packet);
+}
+
 void handle_ipv4(const uint8_t *payload, uint32_t packet_length) {
   assert(packet_length > 4);
+
+  uint16_t saved_checksum = *(uint16_t *)(payload + 10);
+  *(uint16_t *)(payload + 10) = 0;
+  uint16_t calc_checksum = ip_checksum((uint8_t *)payload, 20);
+  *(uint16_t *)(payload + 10) = saved_checksum;
+  assert(calc_checksum == saved_checksum);
+
   uint8_t version = (*payload & 0xF0) >> 4;
   uint8_t IHL = (*payload & 0xF);
   kprintf("version: %x\n", version);
diff --git a/network/ipv4.h b/network/ipv4.h
index 294a0ef..f578202 100644
--- a/network/ipv4.h
+++ b/network/ipv4.h
@@ -1,3 +1,5 @@
 #include <stdint.h>
 
 void handle_ipv4(const uint8_t *payload, uint32_t packet_length);
+void send_ipv4_packet(uint32_t ip, uint8_t protocol, const uint8_t *payload,
+                      uint16_t length);
diff --git a/network/udp.c b/network/udp.c
index 29f17e1..23411da 100644
--- a/network/udp.c
+++ b/network/udp.c
@@ -1,8 +1,24 @@
 #include <assert.h>
 #include <network/bytes.h>
+#include <network/ipv4.h>
 #include <network/udp.h>
 #include <socket.h>
 
+void send_udp_packet(struct sockaddr_in *src, const struct sockaddr_in *dst,
+                     const uint8_t *payload, uint16_t payload_length) {
+  uint16_t header[4] = {0};
+  header[0] = src->sin_port;
+  header[1] = dst->sin_port;
+  header[2] = htons(payload_length + 8);
+
+  uint16_t packet_length = sizeof(header) + payload_length;
+  uint8_t *packet = kmalloc(packet_length);
+  memcpy(packet, header, sizeof(header));
+  memcpy(packet + sizeof(header), payload, payload_length);
+  send_ipv4_packet(dst->sin_addr.s_addr, 0x11, packet, packet_length);
+  kfree(packet);
+}
+
 void handle_udp(uint8_t src_ip[4], const uint8_t *payload,
                 uint32_t packet_length) {
   assert(packet_length >= 8);
@@ -10,11 +26,10 @@ void handle_udp(uint8_t src_ip[4], const uint8_t *payload,
   // h_.* means host format((probably) little endian)
   uint16_t n_source_port = *(uint16_t *)payload;
   uint16_t h_source_port = ntohs(n_source_port);
+  (void)h_source_port;
   uint16_t h_dst_port = ntohs(*(uint16_t *)(payload + 2));
   uint16_t h_length = ntohs(*(uint16_t *)(payload + 4));
   assert(h_length == packet_length);
-  kprintf("source_port: %d\n", h_source_port);
-  kprintf("dst_port: %d\n", h_dst_port);
   uint16_t data_length = h_length - 8;
   const uint8_t *data = payload + 8;
 
diff --git a/network/udp.h b/network/udp.h
index 8278b87..c30b8c8 100644
--- a/network/udp.h
+++ b/network/udp.h
@@ -1,3 +1,7 @@
+#include <socket.h>
 #include <stdint.h>
 
-void handle_udp(uint8_t src_ip[4], const uint8_t *payload, uint32_t packet_length);
+void handle_udp(uint8_t src_ip[4], const uint8_t *payload,
+                uint32_t packet_length);
+void send_udp_packet(struct sockaddr_in *src, const struct sockaddr_in *dst,
+                     const uint8_t *payload, uint16_t payload_length);