Chuyên đề Hệ điều hành Linux - Bài 14: Thư viện lập trình - Lê Hà Minh
The development library for iptables userspace
packet queuing.
§ Netfilter provides a mechanism for passing
packets out of the stack for queueing to
userspace, then receiving these packets back
into the kernel with a verdict specifying what to
do with the packets (such as ACCEPT or DROP).
These packets may also be modified in
userspace prior to reinjection back into the
kernel.
packet queuing.
§ Netfilter provides a mechanism for passing
packets out of the stack for queueing to
userspace, then receiving these packets back
into the kernel with a verdict specifying what to
do with the packets (such as ACCEPT or DROP).
These packets may also be modified in
userspace prior to reinjection back into the
kernel.
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30/12/2022
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- Contents n Libipq n Libnet n Libcap
- Libipq £ For each supported protocol, a kernel module called a queue handler may register with Netfilter to perform the mechanics of passing packets to and from userspace. £ The standard queue handler for IPv4 is ip_queue. It is provided as an experimental module with 2.4 kernels, and uses a Netlink socket for kernel/userspace communication. 4 £ Once ip_queue is loaded, IP packets may be selected with iptables and queued for userspace processing via the QUEUE target
- Libipq £ ipq_create_handle(3) Initialise library, return context handle. £ ipq_set_mode(3) Set the queue mode, to copy either packet metadata, or payloads as well as metadata to userspace. £ ipq_read(3) Wait for a queue message to arrive from ip_queue and read it into a buffer. £ ipq_message_type(3) Determine message type in the buffer. 6 £ ipq_get_packet(3) Retrieve a packet message from the buffer.
- Libipq 8
- Libipq £ Install Yum install iptables-devel p Load modules p Compile: gcc -o yourapp yourapp.c –lipq p Run: ./yourapp p Reference: pq_by_example 10
- Libnet £ Install £ Read libnet-primer for more details. 12
- Libpcap £ Read other documents for more details 14
