From 4e10df9a60d96ced321dd2af71da558c6b750078 Mon Sep 17 00:00:00 2001 From: Alexei Starovoitov Date: Mon, 20 Jul 2015 20:34:18 -0700 Subject: 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 Signed-off-by: David S. Miller --- net/core/filter.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 48 insertions(+) (limited to 'net/core') diff --git a/net/core/filter.c b/net/core/filter.c index 247450a5e387..50338071fac4 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1437,6 +1437,50 @@ static const struct bpf_func_proto bpf_get_cgroup_classid_proto = { .arg1_type = ARG_PTR_TO_CTX, }; +static u64 bpf_skb_vlan_push(u64 r1, u64 r2, u64 vlan_tci, u64 r4, u64 r5) +{ + struct sk_buff *skb = (struct sk_buff *) (long) r1; + __be16 vlan_proto = (__force __be16) r2; + + if (unlikely(vlan_proto != htons(ETH_P_8021Q) && + vlan_proto != htons(ETH_P_8021AD))) + vlan_proto = htons(ETH_P_8021Q); + + return skb_vlan_push(skb, vlan_proto, vlan_tci); +} + +const struct bpf_func_proto bpf_skb_vlan_push_proto = { + .func = bpf_skb_vlan_push, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_ANYTHING, + .arg3_type = ARG_ANYTHING, +}; + +static u64 bpf_skb_vlan_pop(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) +{ + struct sk_buff *skb = (struct sk_buff *) (long) r1; + + return skb_vlan_pop(skb); +} + +const struct bpf_func_proto bpf_skb_vlan_pop_proto = { + .func = bpf_skb_vlan_pop, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, +}; + +bool bpf_helper_changes_skb_data(void *func) +{ + if (func == bpf_skb_vlan_push) + return true; + if (func == bpf_skb_vlan_pop) + return true; + return false; +} + static const struct bpf_func_proto * sk_filter_func_proto(enum bpf_func_id func_id) { @@ -1476,6 +1520,10 @@ tc_cls_act_func_proto(enum bpf_func_id func_id) return &bpf_clone_redirect_proto; case BPF_FUNC_get_cgroup_classid: return &bpf_get_cgroup_classid_proto; + case BPF_FUNC_skb_vlan_push: + return &bpf_skb_vlan_push_proto; + case BPF_FUNC_skb_vlan_pop: + return &bpf_skb_vlan_pop_proto; default: return sk_filter_func_proto(func_id); } -- cgit v1.2.3