Handle DHCP

moratorium08 · Aug 15, 2018 · 3e53da1 · 3e53da1
1 parent 11592b0
commit 3e53da1
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Showing 2 changed files with 71 additions and 19 deletions.
diff --git a/dhcp.c b/dhcp.c
@@ -34,14 +34,22 @@ void use(int x) {
     ipaddrs[x].st = IPUsed;
 }
 
+int is_reserverd(unsigned long long haddr, int addr) {
+    IPAddr ad = ipaddrs[addr];
+    if (ad.st != IPReserved) return 0;
+    if (ad.addr != haddr) return 0;
+    ipaddrs[addr].st = IPUsed;
+    return 1;
+}
+
 int reserve(unsigned long long haddr) {
     for (int i = 15; i < 256; i++) {
         IPAddr ad = ipaddrs[i];
         if (ad.addr == haddr) {
             return ip_addr_upper * 0x100 + i;
         }
         if (ad.st == IPAvailable) {
-            ipaddrs[i].st = IPUsed;
+            ipaddrs[i].st = IPReserved;
             ipaddrs[i].addr = haddr;
             return ip_addr_upper * 0x100 + i;
         }
@@ -77,6 +85,38 @@ DHCP *handle_discover(DHCP *d) {
 } 
 
 DHCP *handle_request(DHCP *d) {
+    unsigned int addr = 0;
+    for (int i = 0; i < d->option_num; i++) {
+        DHCPOption op = d->options[i];
+        if (op.type != 50) continue;
+
+        for (int i = 0; i < 4; i++) {
+            addr *= 0x100;
+            addr += (unsigned char)(op.data[i]);
+        }
+
+    }
+
+    printf("%x\n", addr);
+    if (!is_reserverd(d->chaddr, addr & 0xff)) {
+        return NULL;
+    }
     DHCP *dhcp = (DHCP *)malloc(sizeof(DHCP));
+    memset(dhcp, 0, sizeof(DHCP));
+
+    dhcp->type = DHCPAck;
+    dhcp->op = 2;
+    dhcp->htype = 0x1;
+    dhcp->hlen = 0x6;
+    dhcp->ops = d->ops;
+    dhcp->xid = d->xid;
+    dhcp->secs = d->secs;
+    dhcp->flags = d->flags;
+    dhcp->ciaddr = 0;
+    dhcp->yiaddr = addr;
+    dhcp->siaddr = host_ip;
+    dhcp->giaddr = 0;
+    dhcp->chaddr = d->chaddr;
+
     return dhcp;
 }
diff --git a/main.c b/main.c
@@ -539,9 +539,10 @@ int gen_dhcp_packet(DHCP *d, byte * buf) {
     save_big_endian(0x0f04, options + 31, 2);
     save_big_endian(0x686f6765, options + 33, 4);
 
+    save_big_endian(0x3604, options + 37, 2);
+    save_big_endian(IPADDR, options + 39, 4);
 
-
-    save_big_endian(0xff,  options + 37, 1);
+    save_big_endian(0xff,  options + 43, 1);
     return 28 + 16 + 64 + 128 + 64;
 }
 
@@ -932,6 +933,8 @@ int main(int argc, char const *argv[]) {
       }
       else if (e->type == ETYPE_IPv4) {
           print_packet(e);
+
+
           char buf[1024];
           memset(buf, 0, 1024);
 
@@ -945,6 +948,7 @@ int main(int argc, char const *argv[]) {
           e->ipv4->udp->sender_port = e->ipv4->udp->recver_port;
           e->ipv4->udp->recver_port = tmp2;
 
+
           UDP *udp = e->ipv4->udp;
           if (udp->recver_port == 68) {
               DHCP *dhcp = parse_dhcp(udp->data);
@@ -955,27 +959,35 @@ int main(int argc, char const *argv[]) {
               dump_data(bufr);
               switch(dhcp->type) {
                   case DHCPDiscover:
+                      printf("Discover!!\n");
                       d = handle_discover(dhcp);
-                      int size = gen_dhcp_packet(d, dhcp_data);
-                      e->ipv4->udp->length = size;
-                      e->ipv4->udp->data = dhcp_data;
+                      break;
+                  case DHCPRequest:
+                      printf("Request!!\n");
+                      d = handle_request(dhcp);
+                      break;
+                  default:
+                      continue;
+              }
+              if (d == NULL) {
+                  printf("oopps");
+                  continue;
+              }
+              int size = gen_dhcp_packet(d, dhcp_data);
+              e->ipv4->udp->length = size;
+              e->ipv4->udp->data = dhcp_data;
 
-                      e->ipv4->length = size + 36;
+              e->ipv4->length = size + 36;
 
-                      print_dhcp(parse_dhcp(dhcp_data));
+              print_dhcp(parse_dhcp(dhcp_data));
 
-                      e->ipv4->sender_addr = IPADDR;
-                      e->ipv4->recver_addr = 0xffffffff;
+              e->ipv4->sender_addr = IPADDR;
+              e->ipv4->recver_addr = 0xffffffff;
 
-                      gen_ethernet_packet(e, buf);
-                      print_packet(e);
-                      write_a_packet(buf);
-                      dump_data(buf);
-                      break;
-                  default:
-                      printf("yata-\n");
-                      break;
-              }
+              gen_ethernet_packet(e, buf);
+              print_packet(e);
+              write_a_packet(buf);
+              dump_data(buf);
           } else {
               gen_ethernet_packet(e, buf);
               write_a_packet(buf);