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minexew
126 lines
2.8 KiB
HolyC
126 lines
2.8 KiB
HolyC
// vim: set ft=c:
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// Not a Network Layer protocol, but it is encapsulated in L2 frames, which makes it L3 for our purposes
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#define ARP_REQUEST 0x01
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#define ARP_REPLY 0x02
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class CArpHeader {
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U16 htype;
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U16 ptype;
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U8 hlen;
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U8 plen;
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U16 oper;
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U8 sha[6];
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U32 spa;
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U8 tha[6];
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U32 tpa;
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};
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class CArpCacheEntry {
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CArpCacheEntry* next;
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U32 ip;
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U8 mac[6];
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};
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// Stored in network order
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static U32 arp_my_ipv4_n = 0;
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// TODO: use a Hash table
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static CArpCacheEntry* arp_cache = NULL;
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// IPs are in network order
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I64 ArpSend(U16 oper, U8* dest_mac, U8* sender_mac, U32 sender_ip_n, U8* target_mac, U32 target_ip_n) {
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U8* frame;
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I64 index = EthernetFrameAlloc(&frame, sender_mac, dest_mac,
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ETHERTYPE_ARP, sizeof(CArpHeader), 0);
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if (index < 0)
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return index;
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CArpHeader* hdr = frame;
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hdr->htype = htons(1);
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hdr->ptype = htons(ETHERTYPE_IPV4);
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hdr->hlen = 6;
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hdr->plen = 4;
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hdr->oper = htons(oper);
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MemCpy(hdr->sha, sender_mac, 6);
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hdr->spa = sender_ip_n;
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MemCpy(hdr->tha, target_mac, 6);
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hdr->tpa = target_ip_n;
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return EthernetFrameFinish(index);
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}
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U0 ArpSetIPv4Address(U32 addr) {
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arp_my_ipv4_n = htonl(addr);
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// Broadcast our new address
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ArpSend(ARP_REPLY, eth_broadcast, EthernetGetAddress(), arp_my_ipv4_n, eth_null, arp_my_ipv4_n);
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}
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CArpCacheEntry* ArpCacheFindByIP(U32 ip) {
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CArpCacheEntry* e = arp_cache;
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while (e) {
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if (e->ip == ip)
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return e;
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e = e->next;
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}
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return e;
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}
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CArpCacheEntry* ArpCachePut(U32 ip, U8* mac) {
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CArpCacheEntry* e = ArpCacheFindByIP(ip);
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if (!e) {
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//"ARP: add entry for %08X\n", ip;
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e = MAlloc(sizeof(CArpCacheEntry));
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e->next = arp_cache;
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e->ip = ip;
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MemCpy(e->mac, mac, 6);
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arp_cache = e;
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}
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// FIXME: else replace!
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return e;
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}
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I64 ArpHandler(CEthFrame* eth_frame) {
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if (eth_frame->ethertype != ETHERTYPE_ARP)
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return -1;
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if (eth_frame->length < sizeof(CArpHeader))
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return -1;
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CArpHeader* hdr = eth_frame->data;
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U16 oper = ntohs(hdr->oper);
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//"ARP: htype %d, ptype %d, hlen %d, plen %d, oper %d\n",
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// ntohs(hdr->htype), ntohs(hdr->ptype), hdr->hlen, hdr->plen, oper;
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//" spa %08X, tpa %08X\n", ntohl(hdr->spa), ntohl(hdr->tpa);
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if (ntohs(hdr->htype) != 1 || ntohs(hdr->ptype) != ETHERTYPE_IPV4
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|| hdr->hlen != 6 || hdr->plen != 4)
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return -1;
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if (oper == ARP_REQUEST) {
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// Not too sure about this line, but it seems necessary in WiFi networks,
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// because the wireless device won't hear our Ethernet broadcast when we Request
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//ArpCachePut(ntohl(hdr->spa), hdr->sha);
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if (hdr->tpa == arp_my_ipv4_n) {
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ArpSend(ARP_REPLY, hdr->sha, EthernetGetAddress(), arp_my_ipv4_n, hdr->sha, hdr->spa);
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}
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}
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else if (oper == ARP_REPLY) {
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ArpCachePut(ntohl(hdr->spa), hdr->sha);
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}
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return 0;
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}
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RegisterL3Protocol(ETHERTYPE_ARP, &ArpHandler);
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