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tipc: introduce direct iovec to buffer chain fragmentation function

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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: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jon Paul Maloy 2014-06-25 20:41:34 -05:00 committed by David S. Miller
parent 16e166b88c
commit 067608e9d0
2 changed files with 105 additions and 0 deletions
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102
net/tipc/msg.c
View file

@ -144,6 +144,108 @@ int tipc_buf_append(struct sk_buff **headbuf, struct sk_buff **buf)
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")

3
net/tipc/msg.h
View file

@ -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