mp = ms;
8
mn = mp->m_next;
9
len = mp->m_len;
10
while (mn != NULL) {
11
if (mn->m_len == 0) {
mp->m_next = mn->m_next;
mn->m_next = NULL;
m_free(mn);
} else {
12
len += mn->m_len;
mp = mn;
}
mn = mp->m_next;
}
1
While true, removes packets from the pending queue and has the device
transmit the packets.
2
Calls the
IF_DEQUEUE
macro to remove an entry from the output queue.
The output queue is referenced through the
if_snd
member of the
ifnet
data structure for this device. The memory buffer information is
the instance of the
mbuf
data structure called
m
.
3
Checks that the total packet length is less than the number of bytes left
in the transmit first-in/first-out (FIFO).
4
Eliminates any zero-length segments. The
ms mbuf
pointer will point to
the first buffer segment with data.
5
Skips over any leading zero-length segments.
6
Stores the next memory buffer in the chain of
mbuf
data structures in
the
ms mbuf
pointer. The
m_next
member stores the next memory
buffer in the chain. Network device drivers typically reference this
member through the alternate name
m_next
, which is defined in the
mbuf.h
header file.
7
If this is a zero-length transmit, calls the
m_freem( )
routine to free the
mbuf
buffer chain.
8
Stores the first memory buffer in the chain of
mbuf
data structures in
the
mp mbuf
pointer.
9
Stores the next memory buffer in the chain of
mbuf
data structures in
the
mn mbuf
pointer.
10
Stores the amount of data in the
mp mbuf
in the
len
variable. The
mh_len
member of the
mbuf
data structure pointer stores the amount
of data in this
mbuf
data structure. Network device drivers typically
reference this member through the alternate name
m_len
, which is
defined in the
mbuf.h
header file.
11
While the
mn mbuf
is not NULL, manipulates the
mh_len
and
mh_next
members of the
mbuf
data structure to eliminate any zero-length buffers
Implementing the Start Section 9–5
