ip.cc

南京航空航天大学开发的一个类Unix和Linux的操作系统,好不好看看就知道了,

#include "root.h"
#include <lib/string.h>
#include "ip.h"
#include "udp.h"
#include "tcp.h"
#include "icmp.h"
#include "raw.h"
#include "arp.h"

ipstat_t ipstat;

void ipaddhead(pkt_t *pkt, u8_t proto, u32_t saddr, u32_t daddr)
{
        static u32_t initippktid;

	pkt->addhead(sizeof(iphdr_t));
	iphdr_t *ih = (iphdr_t*)pkt->data;
	ih->ihl = sizeof(iphdr_t) >> 2;
	ih->ver = IPVER4;
	ih->tos = 0;
	ih->totlen = htons(pkt->datalen);
	ih->id = htons(initippktid++);
	ih->frag = htons(0);
	ih->ttl = 255;
	ih->proto = proto;  
	ih->chksum = 0; 
	ih->saddr = saddr;
	ih->daddr = daddr;
        ih->chksum = ipchksum(ih, sizeof(iphdr_t));
}

/* 1) this function is only used to transmit packet generated by local host 
   2) upper protocol layer _must_ guarantee the size of packet sent by local
      host doesn't exceed mtu.  */
int ipoutput(pkt_t * pkt, u8_t proto, u32_t saddr, u32_t daddr, u16_t *chksum)
{
	netdev_t * netdev;
	u32_t nexthop;
	int e = selectroute(daddr, &netdev, &nexthop);
	if (e) {
		printd("ipoutput:selectroute failed\n");
	        delpkt(pkt);	
		return e;
	}
	if (saddr == INADDRANY)
		saddr = netdev->praddr;
	/* we do the tcp chksum until the saddr is resovled */
	if (chksum) {
		assert(*chksum == 0);
		*chksum = ipchksumpseudo(saddr, daddr, proto, pkt->datalen, pkt->data);
	}
	ipaddhead(pkt, proto, saddr, daddr);
	assert(pkt->datalen <= netdev->mtu);
        return netdev->output(pkt, nexthop);
}

void ipforward(pkt_t * pkt)
{
	iphdr_t * ih = (iphdr_t*) pkt->data;
	netdev_t *netdev;
	u32_t nexthop;
	int e = selectroute(ih->daddr, &netdev, &nexthop);
	if (e) {
		printf("ipforward failed\n");
		delpkt(pkt);
		return;
	}
	netdev->output(pkt, nexthop);
}

void ipinput(pkt_t *pkt)
{
	iphdr_t *ih = (iphdr_t*) pkt->data;
	ipstat.total++;

	debug(NETFLOWDBG, "saddr=%s daddr=%s\n", inetntoa(ih->saddr), inetntoa(ih->daddr));
	/* do some check */
	if (ih->ver != IPVER4) {
		ipstat.badver++;
		printd("bad version number\n");
		delpkt(pkt);
		return;
	}
	if (ih->headlen() != sizeof(iphdr_t)) {
		printd("don't support IP options yet\n");
		delpkt(pkt);
		return;
	}
	if (ipchksum(ih, ih->headlen())) {
		ipstat.badchksum++;
		printd("bad check sum");
		delpkt(pkt);
		return;
	}
	if (ntohs(ih->totlen) < pkt->datalen)
		pkt->trimto(ntohs(ih->totlen));
	/* reassemble the packet if needed */
        if (ih->fraged()) {
                if (!(pkt = ipreass(pkt)))
                        return;
        } 
	/* if the packet is not for this host, forward it */
	if (!tothishost(ih->daddr)) {
		ipforward(pkt);
		return;
	}
	/* deliver the packet to upper protocol */
	switch (ih->proto) {
		case IPPROTOTCP:
    			tcpinput(pkt);
    			return;
		case IPPROTOUDP:
    			udpinput(pkt);
    			return;
		case IPPROTOICMP:
    			if (icmpinput(pkt))
				return;
	}
	if (rawinput(pkt))
		return;
	printd("ipinput:unknown protocol %d\n", ih->proto); 
	icmpoutput(pkt, ICTDSTUNREACH, ICCPROTOUNREACH);
	delpkt(pkt);
}