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author | 2018-10-02 13:35:36 -0700 | |
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committer | 2018-10-03 02:53:47 +0200 | |
commit | 6acc9b432e6714d72d7d77ec7c27f6f8358d0c71 (patch) | |
tree | 1b5ac6b607e8d88a815c8b88d795e71a18260f31 /kernel/bpf | |
parent | bpf: Add reference tracking to verifier (diff) | |
download | linux-6acc9b432e6714d72d7d77ec7c27f6f8358d0c71.tar.gz linux-6acc9b432e6714d72d7d77ec7c27f6f8358d0c71.tar.bz2 linux-6acc9b432e6714d72d7d77ec7c27f6f8358d0c71.zip |
bpf: Add helper to retrieve socket in BPF
This patch adds new BPF helper functions, bpf_sk_lookup_tcp() and
bpf_sk_lookup_udp() which allows BPF programs to find out if there is a
socket listening on this host, and returns a socket pointer which the
BPF program can then access to determine, for instance, whether to
forward or drop traffic. bpf_sk_lookup_xxx() may take a reference on the
socket, so when a BPF program makes use of this function, it must
subsequently pass the returned pointer into the newly added sk_release()
to return the reference.
By way of example, the following pseudocode would filter inbound
connections at XDP if there is no corresponding service listening for
the traffic:
struct bpf_sock_tuple tuple;
struct bpf_sock_ops *sk;
populate_tuple(ctx, &tuple); // Extract the 5tuple from the packet
sk = bpf_sk_lookup_tcp(ctx, &tuple, sizeof tuple, netns, 0);
if (!sk) {
// Couldn't find a socket listening for this traffic. Drop.
return TC_ACT_SHOT;
}
bpf_sk_release(sk, 0);
return TC_ACT_OK;
Signed-off-by: Joe Stringer <joe@wand.net.nz>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel/bpf')
-rw-r--r-- | kernel/bpf/verifier.c | 8 |
1 files changed, 7 insertions, 1 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index cd0d8bc00bd1..73c81bef6ae8 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -153,6 +153,12 @@ static const struct bpf_verifier_ops * const bpf_verifier_ops[] = { * PTR_TO_MAP_VALUE, PTR_TO_SOCKET_OR_NULL becomes PTR_TO_SOCKET when the type * passes through a NULL-check conditional. For the branch wherein the state is * changed to CONST_IMM, the verifier releases the reference. + * + * For each helper function that allocates a reference, such as + * bpf_sk_lookup_tcp(), there is a corresponding release function, such as + * bpf_sk_release(). When a reference type passes into the release function, + * the verifier also releases the reference. If any unchecked or unreleased + * reference remains at the end of the program, the verifier rejects it. */ /* verifier_state + insn_idx are pushed to stack when branch is encountered */ @@ -300,7 +306,7 @@ static bool arg_type_is_refcounted(enum bpf_arg_type type) */ static bool is_release_function(enum bpf_func_id func_id) { - return false; + return func_id == BPF_FUNC_sk_release; } /* string representation of 'enum bpf_reg_type' */ |