1 Commits

Author	SHA1	Message	Date
Daniel Borkmann	7d1d65cb84	net: sched: cls_bpf: add BPF-based classifier ... This work contains a lightweight BPF-based traffic classifier that can serve as a flexible alternative to ematch-based tree classification, i.e. now that BPF filter engine can also be JITed in the kernel. Naturally, tc actions and policies are supported as well with cls_bpf. Multiple BPF programs/filter can be attached for a class, or they can just as well be written within a single BPF program, that's really up to the user how he wishes to run/optimize the code, e.g. also for inversion of verdicts etc. The notion of a BPF program's return/exit codes is being kept as follows: 0: No match -1: Select classid given in "tc filter ..." command else: flowid, overwrite the default one As a minimal usage example with iproute2, we use a 3 band prio root qdisc on a router with sfq each as leave, and assign ssh and icmp bpf-based filters to band 1, http traffic to band 2 and the rest to band 3. For the first two bands we load the bytecode from a file, in the 2nd we load it inline as an example: echo 1 > /proc/sys/net/core/bpf_jit_enable tc qdisc del dev em1 root tc qdisc add dev em1 root handle 1: prio bands 3 priomap 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 tc qdisc add dev em1 parent 1:1 sfq perturb 16 tc qdisc add dev em1 parent 1:2 sfq perturb 16 tc qdisc add dev em1 parent 1:3 sfq perturb 16 tc filter add dev em1 parent 1: bpf run bytecode-file /etc/tc/ssh.bpf flowid 1:1 tc filter add dev em1 parent 1: bpf run bytecode-file /etc/tc/icmp.bpf flowid 1:1 tc filter add dev em1 parent 1: bpf run bytecode-file /etc/tc/http.bpf flowid 1:2 tc filter add dev em1 parent 1: bpf run bytecode "`bpfc -f tc -i misc.ops`" flowid 1:3 BPF programs can be easily created and passed to tc, either as inline 'bytecode' or 'bytecode-file'. There are a couple of front-ends that can compile opcodes, for example: 1) People familiar with tcpdump-like filters: tcpdump -iem1 -ddd port 22 | tr '\n' ',' > /etc/tc/ssh.bpf 2) People that want to low-level program their filters or use BPF extensions that lack support by libpcap's compiler: bpfc -f tc -i ssh.ops > /etc/tc/ssh.bpf ssh.ops example code: ldh [12] jne #0x800, drop ldb [23] jneq #6, drop ldh [20] jset #0x1fff, drop ldxb 4 * ([14] & 0xf) ldh [%x + 14] jeq #0x16, pass ldh [%x + 16] jne #0x16, drop pass: ret #-1 drop: ret #0 It was chosen to load bytecode into tc, since the reverse operation, tc filter list dev em1, is then able to show the exact commands again. Possible follow-up work could also include a small expression compiler for iproute2. Tested with the help of bmon. This idea came up during the Netfilter Workshop 2013 in Copenhagen. Also thanks to feedback from Eric Dumazet! Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Cc: Thomas Graf <tgraf@suug.ch> Signed-off-by: David S. Miller <davem@davemloft.net>	2013-10-29 17:33:17 -04:00