ip_output_dummy.c

一个基于linux的TCP/IP协议栈的实现

/* ip_output_dummy.c
 * [e-mail]
 * 2006-09-09
 */

#include "myip.h"
#include "dev_dummy.h"
#include "log.h"
#include "dummy_ipv4.h"

int ip_append_data_dummy( struct sock *sk, void *from, int length, 
				int transhdrlen, struct rtable *rt, unsigned int flags )
{
	int ipheaderlen = 0;		//the length of dummy ip header
	int alloclen = length + transhdrlen + ipheaderlen;
	struct sk_buff *skb;
	int err;
	
	PR_DEBUG( "copy the sending data to a sk_buff!\n" );

	if( (skb = skb_peek_tail(&sk->sk_write_queue)) == NULL ){
		if( atomic_read( &sk->sk_wmem_alloc ) <= 2 * sk->sk_sndbuf )
			skb = sock_wmalloc(sk, alloclen + 15, 1, sk->sk_allocation);
		if (unlikely(skb == NULL)){
			PR_ERR( "failed to allocate a sk_buff!\n");
			err = -ENOBUFS;
		}
	}
	if (skb == NULL)
		goto error;

	err = -EFAULT;
	skb_put( skb, alloclen );
	if( skb_store_bits( skb, 0, DUMMY_HEADER, transhdrlen ) < 0 ){
		PR_ERR( "copy DUMMY_HEADER to skb error!\n" );
		goto error;
	}
	if( skb_store_bits( skb, transhdrlen, ((struct iovec *)from)->iov_base, length ) < 0 ){
		PR_ERR( "copy data to skb error!\n" );
		goto error;
	}

	err = -ENODEV;
	if( (skb->dev = dev_get_by_name( "mylo" )) == NULL )
		goto error;
	__skb_queue_tail( &sk->sk_write_queue, skb );
	return 0;
error:
	return err;
}

static inline int ip_finish_output2_dummy(struct sk_buff *skb)
{
	PR_DEBUG( "call skb->dst->neighbour->output!\n" );
	return neigh_resolve_output_dummy( skb );
}

static inline int ip_finish_output_dummy( struct sk_buff *skb )
{
	PR_DEBUG( "call ip_finish_output2!\n" );
	return ip_finish_output2_dummy( skb );
}

int ip_output_dummy( struct sk_buff *skb )
{
	PR_DEBUG( "call ip_finish_output!\n" );
	skb->protocol = htons(ETH_P_IP);
	return ip_finish_output_dummy( skb );
}

static inline int dst_output_dummy(struct sk_buff *skb)
{
	PR_DEBUG( "call the function skb->dst->output!\n" );
	return ip_output_dummy( skb );
}

int ip_push_pending_frames_dummy( struct sock *sk )
{
	struct sk_buff *skb;
	int rc = 0;

	PR_DEBUG( "start to send the ip packet out!\n" );
	if( (skb = __skb_dequeue(&sk->sk_write_queue)) == NULL )
		return rc;
	if( (rc = dst_output_dummy( skb )) != 0 ){
		PR_ERR( "unable to send out the packet!\n" );
		dev_put( skb->dev );
		skb_orphan( skb );
		kfree( skb );
	}
	return rc;
}

EXPORT_SYMBOL_GPL( ip_append_data_dummy );
EXPORT_SYMBOL_GPL( ip_push_pending_frames_dummy );