dummy_ipv4.c

一个基于linux的TCP/IP协议栈的实现

/* dummy_ipv4.c
 * [e-mail]
 * 2006-09-04
 */

#include <net/inet_sock.h>
#include <net/sock.h>
#include <linux/in.h>
#include <net/tcp_states.h>

#include "log.h"
#include "dummy_ipv4.h"
#include "af_inet.h"
#include "route_dummy.h"
#include "myip.h"

static struct sock *dummy_sock;

static int dummy_init( struct sock *sk )
{
	PR_DEBUG( "initialize the dummy sock!\n" );
	return 0;
}

static void dummy_hash( struct sock *sk )
{
	dummy_sock = sk;
	PR_DEBUG( "hash the dummy sock!\n" );
}

static void dummy_unhash( struct sock *sk )
{
	dummy_sock = NULL;
	PR_DEBUG( "unhash the dummy sock!\n");
}

static void dummy_close(struct sock *sk, long timeout)
{
	PR_DEBUG( "close the dummy sock!\n");
	sk_common_release(sk);
}

static int dummy_sendmsg(struct kiocb *iocb, struct sock *sk, 
				struct msghdr *msg, size_t len)
{
	struct inet_sock *inet = inet_sk(sk);
	int connected = 0;
	u32 daddr;
	u16 dport;
	struct rtable *rt = NULL;
	sa_family_t family;
	int err;

	PR_DEBUG( "send a dummy packet, len: %d\n", len );
#ifdef MYIPV4_DEBUG
	family = DEBUG_AF_INET;
#else
	family = AF_INET;
#endif
	if( len > 0xFF ){
		PR_ERR( "the max size of packet is 0xFF in dummy protocol!\n" );
		return -EMSGSIZE;
	}

	if( msg->msg_flags & MSG_OOB ){
		PR_ERR( "not support MSG_OOB in dummy protocol!\n");
		return -EOPNOTSUPP;
	}
	if( msg->msg_name ){
		struct sockaddr_in * usin = (struct sockaddr_in*)msg->msg_name;
		if( msg->msg_namelen < sizeof(*usin) ){
			PR_ERR( "invalid argument!, the msg len is: %d\n", msg->msg_namelen );
			return -EINVAL;
		}
		if( usin->sin_family != family ){
			if (usin->sin_family != AF_UNSPEC){
				PR_ERR( "not support the family: %d\n", usin->sin_family );
				return -EAFNOSUPPORT;
			}
		}
		daddr = usin->sin_addr.s_addr;
		dport = usin->sin_port;
	}else{
		if (sk->sk_state != TCP_ESTABLISHED){
			PR_ERR( "require destination address!\n" );
			return -EDESTADDRREQ;
		}
		daddr = inet->daddr;
		dport = inet->dport;
		connected = 1;
  	}

	{
		struct flowi fl = {
					 .proto = IPPROTO_DUMMY,
					 .uli_u = { .ports =
							 { .sport = inet->sport, .dport = dport } } };
		err = ip_route_output_flow_dummy(&rt, &fl, sk, !(msg->msg_flags & MSG_DONTWAIT) );
		if (err)
			goto out;
	}

	ip_append_data_dummy( sk, msg->msg_iov, len, DUMMY_HEADER_LEN, rt, msg->msg_flags );
	err =  ip_push_pending_frames_dummy( sk );
out:
	return err;
}

static int dummy_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
				size_t len, int noblock, int flags, int *addr_len)
{
	struct sk_buff *skb;
	int err = -EINVAL;
	int copied;

	PR_DEBUG( "dummy_recvmsg!\n" );
	skb = skb_recv_datagram(sk, flags, noblock, &err);
	if( !skb )
		goto out;

	PR_DEBUG( "get the skb: %p\n", skb );

	copied = skb->len - DUMMY_HEADER_LEN;
	if (copied > len) {
		copied = len;
		msg->msg_flags |= MSG_TRUNC;
	}

	err = skb_copy_datagram_iovec(skb, DUMMY_HEADER_LEN, msg->msg_iov, copied);
	skb_free_datagram(sk, skb);
out:
  	return err;
}

static int dummy_get_port(struct sock *sk, unsigned short snum)
{
	unsigned short port = 2048;
	struct inet_sock *inet = inet_sk(sk);
	
	PR_DEBUG( "get the port of dummy sock: 2048\n");
	inet->num = port;
	return 0;
}

struct proto dummy_prot = 
{
	.name = "dummy",
	.owner = THIS_MODULE,
	.init = dummy_init,
	.hash = dummy_hash,
	.unhash = dummy_unhash,
	.close = dummy_close,
	.sendmsg =	dummy_sendmsg,
	.recvmsg =	dummy_recvmsg,
	.get_port =	dummy_get_port,	
	.obj_size =	sizeof( struct inet_sock ),
};

static struct sock *dummy_v4_lookup( void )
{
	if( dummy_sock != NULL )
		return dummy_sock;
	return NULL;
}

int dummy_rcv( struct sk_buff *skb )
{
	struct sock *sk;

	PR_DEBUG( "dummy_rcv!\n" );
	
	sk = dummy_v4_lookup();

	if (sk != NULL) {
		if( sock_queue_rcv_skb(sk, skb)<0 ){
			kfree_skb( skb );
			return -1;
		}
		PR_DEBUG( "get the socket!\n" );
		return 0;
	}
	PR_ERR( "can't find the socket to receive the data!\n");
	kfree_skb( skb );
	return -1;
}

EXPORT_SYMBOL_GPL( dummy_prot );
EXPORT_SYMBOL_GPL( dummy_rcv );