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authorAlexei Starovoitov <ast@plumgrid.com>2015-07-20 20:34:18 -0700
committerDavid S. Miller <davem@davemloft.net>2015-07-20 20:52:31 -0700
commit4e10df9a60d96ced321dd2af71da558c6b750078 (patch)
tree6a913ab31a28d48de3b3510470320220eb75e6eb /kernel/bpf/core.c
parentf3120acc7851bffd1cd15acd044b7fa6fa520e75 (diff)
downloadlinux-sh-4e10df9a60d96ced321dd2af71da558c6b750078.tar.gz
bpf: introduce bpf_skb_vlan_push/pop() helpers
Allow eBPF programs attached to TC qdiscs call skb_vlan_push/pop via helper functions. These functions may change skb->data/hlen which are cached by some JITs to improve performance of ld_abs/ld_ind instructions. Therefore JITs need to recognize bpf_skb_vlan_push/pop() calls, re-compute header len and re-cache skb->data/hlen back into cpu registers. Note, skb->data/hlen are not directly accessible from the programs, so any changes to skb->data done either by these helpers or by other TC actions are safe. eBPF JIT supported by three architectures: - arm64 JIT is using bpf_load_pointer() without caching, so it's ok as-is. - x64 JIT re-caches skb->data/hlen unconditionally after vlan_push/pop calls (experiments showed that conditional re-caching is slower). - s390 JIT falls back to interpreter for now when bpf_skb_vlan_push() is present in the program (re-caching is tbd). These helpers allow more scalable handling of vlan from the programs. Instead of creating thousands of vlan netdevs on top of eth0 and attaching TC+ingress+bpf to all of them, the program can be attached to eth0 directly and manipulate vlans as necessary. Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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