recvmmsg¶

Intro¶

recvmmsg - Receive multiple messages on a socket

Description¶

The recvmmsg() system call is used to receive multiple messages from a socket, similar to recvmsg(), but allows passing a user-space array to retrieve multiple messages into different buffers with a single call, instead of having to call the function multiple times.

There are several advantages to using recvmmsg(): - It is much faster, because it can receive multiple messages at once, thus avoiding the need for multiple system calls. - It can be used for better network performance, since it does fewer system calls, meaning less context switches from user-space to kernel-space. - It can be used to receive multiple messages from different sockets (as opposed to recvmsg(), which receives from only one)

There are also a few drawbacks to using recvmmsg(): - It is not suitable for small messages, since the overhead for using it is higher than that of using the single message system call (recvmsg()) - If the socket is set to non-blocking, recvmmsg() will return an error if there are not enough messages in the queue, whereas recvmsg() would return immediately with the messages it has (if any).

Arguments¶

sockfd:int[K] - The file descriptor of the socket.
msgvec:struct mmsghdr*[U] - An array of mmsghdr structures, each one containing a message that recvmmsg() receives into. The caller should ensure that this array is large enough for up to vlen messages.
vlen:unsigned int[K] - The maximum size of the msgvec array.
flags:int[K] - Socket flags, such as MSG_DONTWAIT.
timeout:struct timespec*[K] - If not null, a pointer to a timespec structure to be used for timeouts.

Available Tags¶

K - Originated from kernel-space.
U - Originated from user space (for example, pointer to user space memory used to get it)
TOCTOU - Vulnerable to TOCTOU (time of check, time of use)
OPT - Optional argument - might not always be available (passed with null value)

Hooks¶

sys_recvmmsg¶

Type¶

kprobe

Purpose¶

To monitor the receipt of multiple messages on a socket.

Example Use Case¶

By using recvmmsg(), multiple file descriptors can be monitored in a single system call, thus avoiding the need for making multiple system calls. This can be useful when working with high-performance applications, such as distributed systems, where a single system call needs to receive many messages at once.

Issues¶

No known issues.

recvmsg() - Receive a message from a socket.
sendmmsg() - Send multiple messages on a socket.

This document was automatically generated by OpenAI and needs review. It might not be accurate and might contain errors. The authors of Tracee recommend that the user reads the "events.go" source file to understand the events and their arguments better.