Commit 067608e9 authored by Jon Paul Maloy's avatar Jon Paul Maloy Committed by David S. Miller
Browse files

tipc: introduce direct iovec to buffer chain fragmentation function 



Fragmentation at message sending is currently performed in two
places in link.c, depending on whether data to be transmitted
is delivered in the form of an iovec or as a big sk_buff. Those
functions are also tightly entangled with the send functions
that are using them.

We now introduce a re-entrant, standalone function, tipc_msg_build2(),
that builds a packet chain directly from an iovec. Each fragment is
sized according to the MTU value given by the caller, and is prepended
with a correctly built fragment header, when needed. The function is
independent from who is calling and where the chain will be delivered,
as long as the caller is able to indicate a correct MTU.

The function is tested, but not called by anybody yet. Since it is
incompatible with the existing tipc_msg_build(), and we cannot yet
remove that function, we have given it a temporary name.

Signed-off-by: default avatarJon Maloy <jon.maloy@ericsson.com>
Reviewed-by: default avatarErik Hugne <erik.hugne@ericsson.com>
Reviewed-by: default avatarYing Xue <ying.xue@windriver.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 16e166b8

net/tipc/msg.c

+102 −0
Original line number Diff line number Diff line
@@ -144,6 +144,108 @@ out_free: 
	return 0;

}





/**

 * tipc_msg_build2 - create buffer chain containing specified header and data

 * @mhdr: Message header, to be prepended to data

 * @iov: User data

 * @offset: Posision in iov to start copying from

 * @dsz: Total length of user data

 * @pktmax: Max packet size that can be used

 * @chain: Buffer or chain of buffers to be returned to caller

 * Returns message data size or errno: -ENOMEM, -EFAULT

 */

int tipc_msg_build2(struct tipc_msg *mhdr, struct iovec const *iov,

		    int offset, int dsz, int pktmax , struct sk_buff **chain)

{

	int mhsz = msg_hdr_sz(mhdr);

	int msz = mhsz + dsz;

	int pktno = 1;

	int pktsz;

	int pktrem = pktmax;

	int drem = dsz;

	struct tipc_msg pkthdr;

	struct sk_buff *buf, *prev;

	char *pktpos;

	int rc;



	msg_set_size(mhdr, msz);



	/* No fragmentation needed? */

	if (likely(msz <= pktmax)) {

		buf = tipc_buf_acquire(msz);

		*chain = buf;

		if (unlikely(!buf))

			return -ENOMEM;

		skb_copy_to_linear_data(buf, mhdr, mhsz);

		pktpos = buf->data + mhsz;

		if (!dsz || !memcpy_fromiovecend(pktpos, iov, offset, dsz))

			return dsz;

		rc = -EFAULT;

		goto error;

	}



	/* Prepare reusable fragment header */

	tipc_msg_init(&pkthdr, MSG_FRAGMENTER, FIRST_FRAGMENT,

		      INT_H_SIZE, msg_destnode(mhdr));

	msg_set_size(&pkthdr, pktmax);

	msg_set_fragm_no(&pkthdr, pktno);



	/* Prepare first fragment */

	*chain = buf = tipc_buf_acquire(pktmax);

	if (!buf)

		return -ENOMEM;

	pktpos = buf->data;

	skb_copy_to_linear_data(buf, &pkthdr, INT_H_SIZE);

	pktpos += INT_H_SIZE;

	pktrem -= INT_H_SIZE;

	skb_copy_to_linear_data_offset(buf, INT_H_SIZE, mhdr, mhsz);

	pktpos += mhsz;

	pktrem -= mhsz;



	do {

		if (drem < pktrem)

			pktrem = drem;



		if (memcpy_fromiovecend(pktpos, iov, offset, pktrem)) {

			rc = -EFAULT;

			goto error;

		}

		drem -= pktrem;

		offset += pktrem;



		if (!drem)

			break;



		/* Prepare new fragment: */

		if (drem < (pktmax - INT_H_SIZE))

			pktsz = drem + INT_H_SIZE;

		else

			pktsz = pktmax;

		prev = buf;

		buf = tipc_buf_acquire(pktsz);

		if (!buf) {

			rc = -ENOMEM;

			goto error;

		}

		prev->next = buf;

		msg_set_type(&pkthdr, FRAGMENT);

		msg_set_size(&pkthdr, pktsz);

		msg_set_fragm_no(&pkthdr, ++pktno);

		skb_copy_to_linear_data(buf, &pkthdr, INT_H_SIZE);

		pktpos = buf->data + INT_H_SIZE;

		pktrem = pktsz - INT_H_SIZE;



	} while (1);



	msg_set_type(buf_msg(buf), LAST_FRAGMENT);

	return dsz;

error:

	kfree_skb_list(*chain);

	*chain = NULL;

	return rc;

}



/**

 * tipc_msg_bundle(): Append contents of a buffer to tail of an existing one

 * @bbuf: the existing buffer ("bundle")

net/tipc/msg.h

+3 −0
Original line number Diff line number Diff line
@@ -737,4 +737,7 @@ bool tipc_msg_bundle(struct sk_buff *bbuf, struct sk_buff *buf, u32 mtu); 


bool tipc_msg_make_bundle(struct sk_buff **buf, u32 mtu, u32 dnode);



int tipc_msg_build2(struct tipc_msg *mhdr, struct iovec const *iov,

		    int offset, int dsz, int mtu , struct sk_buff **chain);



#endif

CRA Git | Maintained and supported by SUSTech CRA and CCSE