/* --- CCDN ，这个是真正的包处理函数，重点是判断mac包头的type字段，分ip包和arp包进行处理 */
void process_packet(struct sr_instance* sr, const uint8_t * packet, unsigned int len, const char* interface) {
// uint8_t的定义：typedef unsigned char uint_8, interface应该是指进来的端口名，例如eth0之类的吧
/*
printf("\n--- Received Packet on iface: %s ---\n", interface);
print_packet((uint8_t*)packet, len);
printf("&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&\n");
*/
if (iface_is_active(get_router_state(sr), (char*)interface) == 0) {
/* drop the packet */
return;
}
/* REQUIRES */
assert(sr);
assert(packet);
assert(interface);
eth_hdr *ether_hdr = (eth_hdr *) packet;
switch(ntohs(ether_hdr->eth_type)) {
case ETH_TYPE_IP:
printf(" ** -> Received IP packet of length %d\n", len);
process_ip_packet(sr, packet, len, interface);
break;
case ETH_TYPE_ARP:
printf(" ** -> Received ARP packet of length %d\n", len);
process_arp_packet(sr, packet, len, interface);
break;
default: break;
}
}
void sr_handlepacket(struct sr_instance* sr,
uint8_t * packet/* lent */,
unsigned int len,
char* interface/* lent */)
{
/* REQUIRES */
assert(sr);
assert(packet);
assert(interface);
printf("Received packet of length %d \n",len);
/* fill in code here */
/*initializing key variables*/
uint8_t* packet_buffer; /*packet buffer*/
/*struct sr_if* iface;*/ /*interface struct*/
uint16_t checksum,ether_type; /*checksum bit*/
unsigned int packet_len,minlength; /*packet length*/
int ipLen,etherLen,arpLen;
packet_buffer = packet;
packet_len = len;
minlength = sizeof(sr_ethernet_hdr_t);
etherLen = sizeof(sr_ethernet_hdr_t); /*ethernet header size*/
ipLen = sizeof(sr_ip_hdr_t); /*ip header length*/
arpLen = sizeof(sr_arp_hdr_t); /*arp header length*/
if (len > IP_MAXPACKET)
{
perror("Error: invalid packet size");
exit(1);
}
if (len < minlength)
{
perror("Error: packet size too small");
exit(1);
}
/*obtain interface information*/
/*iface = sr_get_interface(sr,interface);*/
/*examining each layer of header*/
/*examine ethernet header*/
sr_ethernet_hdr_t* ether_header = (sr_ethernet_hdr_t*) packet_buffer;
ether_type = ethertype(packet_buffer);
if (ether_type == ethertype_ip) /*IP*/
{
if (process_ip_packet(sr, packet, len, interface) < 0) {
fprintf(stderr, "Error processing IP datagram\n");
}
}
else if (ether_type == ethertype_arp) /*ARP*/
{
if (process_arp_packet(sr, packet, len, interface) <0) {
fprintf(stderr, "Error processing ARP packet\n");
}
}
else {
fprintf(stderr, "Error: Unrecognized Ethernet Type: %d\n", ether_type);
}
}/* end sr_ForwardPacket */
