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03e69b508b
This work is similar to commit 4cd3675ebf ("filter: added BPF
random opcode") and adds a possibility for packet sampling in eBPF.
Currently, this is only possible in classic BPF and useful to
combine sampling with f.e. packet sockets, possible also with tc.
Example function proto-type looks like:
u32 (*prandom_u32)(void) = (void *)BPF_FUNC_get_prandom_u32;
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
102 lines
3.1 KiB
C
102 lines
3.1 KiB
C
/* Copyright (c) 2011-2014 PLUMgrid, http://plumgrid.com
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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#include <linux/bpf.h>
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#include <linux/rcupdate.h>
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#include <linux/random.h>
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/* If kernel subsystem is allowing eBPF programs to call this function,
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* inside its own verifier_ops->get_func_proto() callback it should return
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* bpf_map_lookup_elem_proto, so that verifier can properly check the arguments
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*
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* Different map implementations will rely on rcu in map methods
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* lookup/update/delete, therefore eBPF programs must run under rcu lock
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* if program is allowed to access maps, so check rcu_read_lock_held in
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* all three functions.
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*/
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static u64 bpf_map_lookup_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
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{
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/* verifier checked that R1 contains a valid pointer to bpf_map
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* and R2 points to a program stack and map->key_size bytes were
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* initialized
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*/
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struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
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void *key = (void *) (unsigned long) r2;
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void *value;
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WARN_ON_ONCE(!rcu_read_lock_held());
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value = map->ops->map_lookup_elem(map, key);
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/* lookup() returns either pointer to element value or NULL
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* which is the meaning of PTR_TO_MAP_VALUE_OR_NULL type
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*/
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return (unsigned long) value;
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}
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const struct bpf_func_proto bpf_map_lookup_elem_proto = {
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.func = bpf_map_lookup_elem,
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.gpl_only = false,
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.ret_type = RET_PTR_TO_MAP_VALUE_OR_NULL,
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.arg1_type = ARG_CONST_MAP_PTR,
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.arg2_type = ARG_PTR_TO_MAP_KEY,
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};
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static u64 bpf_map_update_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
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{
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struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
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void *key = (void *) (unsigned long) r2;
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void *value = (void *) (unsigned long) r3;
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WARN_ON_ONCE(!rcu_read_lock_held());
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return map->ops->map_update_elem(map, key, value, r4);
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}
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const struct bpf_func_proto bpf_map_update_elem_proto = {
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.func = bpf_map_update_elem,
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.gpl_only = false,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_CONST_MAP_PTR,
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.arg2_type = ARG_PTR_TO_MAP_KEY,
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.arg3_type = ARG_PTR_TO_MAP_VALUE,
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.arg4_type = ARG_ANYTHING,
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};
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static u64 bpf_map_delete_elem(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
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{
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struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
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void *key = (void *) (unsigned long) r2;
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WARN_ON_ONCE(!rcu_read_lock_held());
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return map->ops->map_delete_elem(map, key);
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}
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const struct bpf_func_proto bpf_map_delete_elem_proto = {
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.func = bpf_map_delete_elem,
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.gpl_only = false,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_CONST_MAP_PTR,
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.arg2_type = ARG_PTR_TO_MAP_KEY,
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};
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static u64 bpf_get_prandom_u32(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
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{
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return prandom_u32();
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}
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const struct bpf_func_proto bpf_get_prandom_u32_proto = {
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.func = bpf_get_prandom_u32,
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.gpl_only = false,
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.ret_type = RET_INTEGER,
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};
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