udp.c

嵌入式系统设计与实验教材二源码linux内核移植与编译

	if (connected)
		rt = (struct rtable*)sk_dst_check(sk, 0);

	if (rt == NULL) {
		err = ip_route_output(&rt, daddr, ufh.saddr, tos, ipc.oif);
		if (err)
			goto out;

		err = -EACCES;
		if (rt->rt_flags&RTCF_BROADCAST && !sk->broadcast) 
			goto out;
		if (connected)
			sk_dst_set(sk, dst_clone(&rt->u.dst));
	}

	if (msg->msg_flags&MSG_CONFIRM)
		goto do_confirm;
back_from_confirm:

	ufh.saddr = rt->rt_src;
	if (!ipc.addr)
		ufh.daddr = ipc.addr = rt->rt_dst;
	ufh.uh.len = htons(ulen);
	ufh.uh.check = 0;
	ufh.iov = msg->msg_iov;
	ufh.wcheck = 0;

	/* RFC1122: OK.  Provides the checksumming facility (MUST) as per */
	/* 4.1.3.4. It's configurable by the application via setsockopt() */
	/* (MAY) and it defaults to on (MUST). */

	err = ip_build_xmit(sk,
			    (sk->no_check == UDP_CSUM_NOXMIT ?
			     udp_getfrag_nosum :
			     udp_getfrag),
			    &ufh, ulen, &ipc, rt, msg->msg_flags);

out:
	ip_rt_put(rt);
	if (free)
		kfree(ipc.opt);
	if (!err) {
		UDP_INC_STATS_USER(UdpOutDatagrams);
		return len;
	}
	return err;

do_confirm:
	dst_confirm(&rt->u.dst);
	if (!(msg->msg_flags&MSG_PROBE) || len)
		goto back_from_confirm;
	err = 0;
	goto out;
}

/*
 *	IOCTL requests applicable to the UDP protocol
 */
 
int udp_ioctl(struct sock *sk, int cmd, unsigned long arg)
{
	switch(cmd) 
	{
		case SIOCOUTQ:
		{
			int amount = atomic_read(&sk->wmem_alloc);
			return put_user(amount, (int *)arg);
		}

		case SIOCINQ:
		{
			struct sk_buff *skb;
			unsigned long amount;

			amount = 0;
			spin_lock_irq(&sk->receive_queue.lock);
			skb = skb_peek(&sk->receive_queue);
			if (skb != NULL) {
				/*
				 * We will only return the amount
				 * of this packet since that is all
				 * that will be read.
				 */
				amount = skb->len - sizeof(struct udphdr);
			}
			spin_unlock_irq(&sk->receive_queue.lock);
			return put_user(amount, (int *)arg);
		}

		default:
			return -ENOIOCTLCMD;
	}
	return(0);
}

static __inline__ int __udp_checksum_complete(struct sk_buff *skb)
{
	return (unsigned short)csum_fold(skb_checksum(skb, 0, skb->len, skb->csum));
}

static __inline__ int udp_checksum_complete(struct sk_buff *skb)
{
	return skb->ip_summed != CHECKSUM_UNNECESSARY &&
		__udp_checksum_complete(skb);
}

/*
 * 	This should be easy, if there is something there we
 * 	return it, otherwise we block.
 */

int udp_recvmsg(struct sock *sk, struct msghdr *msg, int len,
		int noblock, int flags, int *addr_len)
{
  	struct sockaddr_in *sin = (struct sockaddr_in *)msg->msg_name;
  	struct sk_buff *skb;
  	int copied, err;

	/*
	 *	Check any passed addresses
	 */
	if (addr_len)
		*addr_len=sizeof(*sin);

	if (flags & MSG_ERRQUEUE)
		return ip_recv_error(sk, msg, len);

	skb = skb_recv_datagram(sk, flags, noblock, &err);
	if (!skb)
		goto out;
  
  	copied = skb->len - sizeof(struct udphdr);
	if (copied > len) {
		copied = len;
		msg->msg_flags |= MSG_TRUNC;
	}

	if (skb->ip_summed==CHECKSUM_UNNECESSARY) {
		err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov,
					      copied);
	} else if (msg->msg_flags&MSG_TRUNC) {
		if (__udp_checksum_complete(skb))
			goto csum_copy_err;
		err = skb_copy_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov,
					      copied);
	} else {
		err = skb_copy_and_csum_datagram_iovec(skb, sizeof(struct udphdr), msg->msg_iov);

		if (err == -EINVAL)
			goto csum_copy_err;
	}

	if (err)
		goto out_free;

	sock_recv_timestamp(msg, sk, skb);

	/* Copy the address. */
	if (sin)
	{
		sin->sin_family = AF_INET;
		sin->sin_port = skb->h.uh->source;
		sin->sin_addr.s_addr = skb->nh.iph->saddr;
		memset(sin->sin_zero, 0, sizeof(sin->sin_zero));
  	}
	if (sk->protinfo.af_inet.cmsg_flags)
		ip_cmsg_recv(msg, skb);
	err = copied;
  
out_free:
  	skb_free_datagram(sk, skb);
out:
  	return err;

csum_copy_err:
	UDP_INC_STATS_BH(UdpInErrors);

	/* Clear queue. */
	if (flags&MSG_PEEK) {
		int clear = 0;
		spin_lock_irq(&sk->receive_queue.lock);
		if (skb == skb_peek(&sk->receive_queue)) {
			__skb_unlink(skb, &sk->receive_queue);
			clear = 1;
		}
		spin_unlock_irq(&sk->receive_queue.lock);
		if (clear)
			kfree_skb(skb);
	}

	skb_free_datagram(sk, skb);

	return -EAGAIN;	
}

int udp_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
{
	struct sockaddr_in *usin = (struct sockaddr_in *) uaddr;
	struct rtable *rt;
	int err;

	
	if (addr_len < sizeof(*usin)) 
	  	return -EINVAL;

	if (usin->sin_family != AF_INET) 
	  	return -EAFNOSUPPORT;

	sk_dst_reset(sk);

	err = ip_route_connect(&rt, usin->sin_addr.s_addr, sk->saddr,
			       RT_CONN_FLAGS(sk), sk->bound_dev_if);
	if (err)
		return err;
	if ((rt->rt_flags&RTCF_BROADCAST) && !sk->broadcast) {
		ip_rt_put(rt);
		return -EACCES;
	}
  	if(!sk->saddr)
	  	sk->saddr = rt->rt_src;		/* Update source address */
	if(!sk->rcv_saddr)
		sk->rcv_saddr = rt->rt_src;
	sk->daddr = rt->rt_dst;
	sk->dport = usin->sin_port;
	sk->state = TCP_ESTABLISHED;
	sk->protinfo.af_inet.id = jiffies;

	sk_dst_set(sk, &rt->u.dst);
	return(0);
}

int udp_disconnect(struct sock *sk, int flags)
{
	/*
	 *	1003.1g - break association.
	 */
	 
	sk->state = TCP_CLOSE;
	sk->daddr = 0;
	sk->dport = 0;
	sk->bound_dev_if = 0;
	if (!(sk->userlocks&SOCK_BINDADDR_LOCK)) {
		sk->rcv_saddr = 0;
		sk->saddr = 0;
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
		memset(&sk->net_pinfo.af_inet6.saddr, 0, 16);
		memset(&sk->net_pinfo.af_inet6.rcv_saddr, 0, 16);
#endif
	}
	if (!(sk->userlocks&SOCK_BINDPORT_LOCK)) {
		sk->prot->unhash(sk);
		sk->sport = 0;
	}
	sk_dst_reset(sk);
	return 0;
}

static void udp_close(struct sock *sk, long timeout)
{
	inet_sock_release(sk);
}

static int udp_queue_rcv_skb(struct sock * sk, struct sk_buff *skb)
{
	/*
	 *	Charge it to the socket, dropping if the queue is full.
	 */

#if defined(CONFIG_FILTER)
	if (sk->filter && skb->ip_summed != CHECKSUM_UNNECESSARY) {
		if (__udp_checksum_complete(skb)) {
			UDP_INC_STATS_BH(UdpInErrors);
			IP_INC_STATS_BH(IpInDiscards);
			ip_statistics[smp_processor_id()*2].IpInDelivers--;
			kfree_skb(skb);
			return -1;
		}
		skb->ip_summed = CHECKSUM_UNNECESSARY;
	}
#endif

	if (sock_queue_rcv_skb(sk,skb)<0) {
		UDP_INC_STATS_BH(UdpInErrors);
		IP_INC_STATS_BH(IpInDiscards);
		ip_statistics[smp_processor_id()*2].IpInDelivers--;
		kfree_skb(skb);
		return -1;
	}
	UDP_INC_STATS_BH(UdpInDatagrams);
	return 0;
}

/*
 *	Multicasts and broadcasts go to each listener.
 *
 *	Note: called only from the BH handler context,
 *	so we don't need to lock the hashes.
 */
static int udp_v4_mcast_deliver(struct sk_buff *skb, struct udphdr *uh,
				 u32 saddr, u32 daddr)
{
	struct sock *sk;
	int dif;

	read_lock(&udp_hash_lock);
	sk = udp_hash[ntohs(uh->dest) & (UDP_HTABLE_SIZE - 1)];
	dif = skb->dev->ifindex;
	sk = udp_v4_mcast_next(sk, uh->dest, daddr, uh->source, saddr, dif);
	if (sk) {
		struct sock *sknext = NULL;

		do {
			struct sk_buff *skb1 = skb;

			sknext = udp_v4_mcast_next(sk->next, uh->dest, daddr,
						   uh->source, saddr, dif);
			if(sknext)
				skb1 = skb_clone(skb, GFP_ATOMIC);

			if(skb1)
				udp_queue_rcv_skb(sk, skb1);
			sk = sknext;
		} while(sknext);
	} else
		kfree_skb(skb);
	read_unlock(&udp_hash_lock);
	return 0;
}

/* Initialize UDP checksum. If exited with zero value (success),
 * CHECKSUM_UNNECESSARY means, that no more checks are required.
 * Otherwise, csum completion requires chacksumming packet body,
 * including udp header and folding it to skb->csum.
 */
static int udp_checksum_init(struct sk_buff *skb, struct udphdr *uh,
			     unsigned short ulen, u32 saddr, u32 daddr)
{
	if (uh->check == 0) {
		skb->ip_summed = CHECKSUM_UNNECESSARY;
	} else if (skb->ip_summed == CHECKSUM_HW) {
		skb->ip_summed = CHECKSUM_UNNECESSARY;
		if (!udp_check(uh, ulen, saddr, daddr, skb->csum))
			return 0;
		NETDEBUG(if (net_ratelimit()) printk(KERN_DEBUG "udp v4 hw csum failure.\n"));
		skb->ip_summed = CHECKSUM_NONE;
	}
	if (skb->ip_summed != CHECKSUM_UNNECESSARY)
		skb->csum = csum_tcpudp_nofold(saddr, daddr, ulen, IPPROTO_UDP, 0);
	/* Probably, we should checksum udp header (it should be in cache
	 * in any case) and data in tiny packets (< rx copybreak).
	 */
	return 0;
}

/*
 *	All we need to do is get the socket, and then do a checksum. 
 */
 
int udp_rcv(struct sk_buff *skb)
{
  	struct sock *sk;
  	struct udphdr *uh;
	unsigned short ulen;
	struct rtable *rt = (struct rtable*)skb->dst;
	u32 saddr = skb->nh.iph->saddr;
	u32 daddr = skb->nh.iph->daddr;
	int len = skb->len;

  	IP_INC_STATS_BH(IpInDelivers);

	/*
	 *	Validate the packet and the UDP length.
	 */
	if (!pskb_may_pull(skb, sizeof(struct udphdr)))
		goto no_header;

	ulen = ntohs(skb->h.uh->len);

	if (ulen > len || ulen < sizeof(*uh))
		goto short_packet;

	if (pskb_trim(skb, ulen))
		goto short_packet;

  	uh = skb->h.uh;

	if (udp_checksum_init(skb, uh, ulen, saddr, daddr) < 0)
		goto csum_error;

	if(rt->rt_flags & (RTCF_BROADCAST|RTCF_MULTICAST))
		return udp_v4_mcast_deliver(skb, uh, saddr, daddr);

	sk = udp_v4_lookup(saddr, uh->source, daddr, uh->dest, skb->dev->ifindex);

	if (sk != NULL) {
		udp_queue_rcv_skb(sk, skb);
		sock_put(sk);
		return 0;
	}

	/* No socket. Drop packet silently, if checksum is wrong */
	if (udp_checksum_complete(skb))
		goto csum_error;

	UDP_INC_STATS_BH(UdpNoPorts);
	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);

	/*
	 * Hmm.  We got an UDP packet to a port to which we
	 * don't wanna listen.  Ignore it.
	 */
	kfree_skb(skb);
	return(0);

short_packet:
	NETDEBUG(if (net_ratelimit()) printk(KERN_DEBUG "UDP: short packet: %d/%d\n", ulen, len));
no_header:
	UDP_INC_STATS_BH(UdpInErrors);
	kfree_skb(skb);
	return(0);

csum_error:
	/* 
	 * RFC1122: OK.  Discards the bad packet silently (as far as 
	 * the network is concerned, anyway) as per 4.1.3.4 (MUST). 
	 */
	NETDEBUG(if (net_ratelimit())
		 printk(KERN_DEBUG "UDP: bad checksum. From %d.%d.%d.%d:%d to %d.%d.%d.%d:%d ulen %d\n",
			NIPQUAD(saddr),
			ntohs(uh->source),
			NIPQUAD(daddr),
			ntohs(uh->dest),
			ulen));
	UDP_INC_STATS_BH(UdpInErrors);
	kfree_skb(skb);
	return(0);
}

static void get_udp_sock(struct sock *sp, char *tmpbuf, int i)
{
	unsigned int dest, src;
	__u16 destp, srcp;

	dest  = sp->daddr;
	src   = sp->rcv_saddr;
	destp = ntohs(sp->dport);
	srcp  = ntohs(sp->sport);
	sprintf(tmpbuf, "%4d: %08X:%04X %08X:%04X"
		" %02X %08X:%08X %02X:%08lX %08X %5d %8d %ld %d %p",
		i, src, srcp, dest, destp, sp->state, 
		atomic_read(&sp->wmem_alloc), atomic_read(&sp->rmem_alloc),
		0, 0L, 0,
		sock_i_uid(sp), 0,
		sock_i_ino(sp),
		atomic_read(&sp->refcnt), sp);
}

int udp_get_info(char *buffer, char **start, off_t offset, int length)
{
	int len = 0, num = 0, i;
	off_t pos = 0;
	off_t begin;
	char tmpbuf[129];

	if (offset < 128) 
		len += sprintf(buffer, "%-127s\n",
			       "  sl  local_address rem_address   st tx_queue "
			       "rx_queue tr tm->when retrnsmt   uid  timeout inode");
	pos = 128;
	read_lock(&udp_hash_lock);
	for (i = 0; i < UDP_HTABLE_SIZE; i++) {
		struct sock *sk;

		for (sk = udp_hash[i]; sk; sk = sk->next, num++) {
			if (sk->family != PF_INET)
				continue;
			pos += 128;
			if (pos <= offset)
				continue;
			get_udp_sock(sk, tmpbuf, i);
			len += sprintf(buffer+len, "%-127s\n", tmpbuf);
			if(len >= length)
				goto out;
		}
	}
out:
	read_unlock(&udp_hash_lock);
	begin = len - (pos - offset);
	*start = buffer + begin;
	len -= begin;
	if(len > length)
		len = length;
	if (len < 0)
		len = 0; 
	return len;
}

struct proto udp_prot = {
 	name:		"UDP",
	close:		udp_close,
	connect:	udp_connect,
	disconnect:	udp_disconnect,
	ioctl:		udp_ioctl,
	setsockopt:	ip_setsockopt,
	getsockopt:	ip_getsockopt,
	sendmsg:	udp_sendmsg,
	recvmsg:	udp_recvmsg,
	backlog_rcv:	udp_queue_rcv_skb,
	hash:		udp_v4_hash,
	unhash:		udp_v4_unhash,
	get_port:	udp_v4_get_port,
};