Many users of an IBM security product, which uses netfilter's NFQUEUE target to process packets in userspace, face a problem of dropped connections during heavy load. Incoming packets are queued and processed by the security module, which does deep packet analysis to decide whether to accept or reject them. However during heavy load, the queue fills up and connections fail when large number of packets get dropped. This patch implements a "failopen" support for NFQUEUE to help keep connections open during such failures. This is achieved by allowing acceptance of packets temporarily when the queue is full, which enables existing connections to be kept open. Failopen is enabled/disabled using a new call - nfq_set_flags(qh, mask, flags), which makes use of two new netlink attributes: NFQA_CFG_MASK - Specifies which flags are being modified. NFQA_CFG_FLAGS - Set/reset the bits for each of those flags. Tests done: ------------ - netperf TCP_STREAM - 64 netperf stress testing to ensure there are no memory leaks - icmp ping - enabling/disabling failopen in the middle of existing connections - checksum verification of transferred files using scp - different flag/mask values to check that code handling NFQA_CFG_MASK works as expected Test results: ------------- Server: ------- # iptables -A INPUT -p tcp -m mac --mac-source 00:00:C9:C6:4F:22 \ -j NFQUEUE --queue-num 0 # Run interceptor program with 50ms delay between packet processing, and also sets qlen to 16. After every read system call, this program tests and read's a config file's contents and calls nfq_set_flags(qh, mask, flags). Client: ------- ---> failopen is disabled on server at this time # netperf -v0 -H 10.0.4.1 TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.0.4.1 (10.0.4.1) port 0 AF_INET 0.16 ---> failopen is enabled on server at this time # netperf -v0 -H 10.0.4.1 TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 10.0.4.1 (10.0.4.1) port 0 AF_INET 2292.82 ---> failopen is disabled on server at this time # scp FILE 10.0.4.1:/tmp FILE 0% 2960KB 88.4KB/s 12:19:37 ETA ---> Enable failopen on server at this time FILE 21% 809MB 44.2MB/s 01:08 ETA ---> Disable failopen on server at this time FILE 23% 903MB 157.4KB/s 5:18:01 ETA ---> Enable failopen on server at this time FILE 100% 3835MB 24.1MB/s 02:39 Changes from rev3: ------------------ 1. Changed flags/mask to big-endian. 2. Use nla_get_be32 instead of nla_data to access flags/masks. 3. Cleaned up some comments. Changes from rev2: ------------------ 1. Changed NFQA_CFG_FAIL_OPEN to generic NFQA_CFG_FLAGS and NFQA_CFG_MASK to support new flags/options in future. 2. Enqueue handler changed to return -ENOSPC on queue-full condition. 3. Do not invoke okfn on -ENOSPC, but process all hooks first. nf_hook_slow has code to handle failopen. Please review. Signed-off-by: Krishna Kumar <krkumar2@xxxxxxxxxx> Signed-off-by: Vivek Kashyap <vivk@xxxxxxxxxx> Signed-off-by: Sridhar Samudrala <samudrala@xxxxxxxxxx> --- -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
