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