CMSG_SPACE - Linux
Overview
The CMSG_SPACE
command provides the memory space initially required for control messages in a socket buffer prior to receiving. This value is a hint and may be rounded up for alignment reasons.
Syntax
CMSG_SPACE(buflen, msgsize)
| Argument | Description |
|—|—|
| buflen | Size of the buffer |
| msgsize | Size of the control message |
Options/Flags
None
Examples
struct msghdr msg;
...
msg.msg_control = malloc(CMSG_SPACE(1024, 2048));
Common Issues
Insufficient Buffer Size
If the buffer size is too small to accommodate the control message, the operation may fail with EINVAL
. Ensure that the buffer is adequately sized for the expected control message.
Integration
CMSG_SPACE
is commonly used in conjunction with the recvmsg()
and sendmsg()
functions to manipulate socket control messages.
Related Commands
CMSG_LEN
CMSG_FIRSTHDR
CMSG_NXTHDR