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| -rw-r--r-- | Documentation/networking/packet_mmap.rst | 9 |
1 files changed, 4 insertions, 5 deletions
diff --git a/Documentation/networking/packet_mmap.rst b/Documentation/networking/packet_mmap.rst index f3646c80b019..500ef60b1b82 100644 --- a/Documentation/networking/packet_mmap.rst +++ b/Documentation/networking/packet_mmap.rst @@ -8,7 +8,7 @@ Abstract ======== This file documents the mmap() facility available with the PACKET -socket interface on 2.4/2.6/3.x kernels. This type of sockets is used for +socket interface. This type of sockets is used for i) capture network traffic with utilities like tcpdump, ii) transmit network traffic, or any other that needs raw @@ -25,12 +25,12 @@ Please send your comments to Why use PACKET_MMAP =================== -In Linux 2.4/2.6/3.x if PACKET_MMAP is not enabled, the capture process is very +Non PACKET_MMAP capture process (plain AF_PACKET) is very inefficient. It uses very limited buffers and requires one system call to capture each packet, it requires two if you want to get packet's timestamp (like libpcap always does). -In the other hand PACKET_MMAP is very efficient. PACKET_MMAP provides a size +On the other hand PACKET_MMAP is very efficient. PACKET_MMAP provides a size configurable circular buffer mapped in user space that can be used to either send or receive packets. This way reading packets just needs to wait for them, most of the time there is no need to issue a single system call. Concerning @@ -252,8 +252,7 @@ PACKET_MMAP setting constraints In kernel versions prior to 2.4.26 (for the 2.4 branch) and 2.6.5 (2.6 branch), the PACKET_MMAP buffer could hold only 32768 frames in a 32 bit architecture or -16384 in a 64 bit architecture. For information on these kernel versions -see http://pusa.uv.es/~ulisses/packet_mmap/packet_mmap.pre-2.4.26_2.6.5.txt +16384 in a 64 bit architecture. Block size limit ---------------- |