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bpf: Allow any port in bpf_bind helper
We want to have a tighter control on what ports we bind to in the BPF_CGROUP_INET{4,6}_CONNECT hooks even if it means connect() becomes slightly more expensive. The expensive part comes from the fact that we now need to call inet_csk_get_port() that verifies that the port is not used and allocates an entry in the hash table for it. Since we can't rely on "snum || !bind_address_no_port" to prevent us from calling POST_BIND hook anymore, let's add another bind flag to indicate that the call site is BPF program. v5: * fix wrong AF_INET (should be AF_INET6) in the bpf program for v6 v3: * More bpf_bind documentation refinements (Martin KaFai Lau) * Add UDP tests as well (Martin KaFai Lau) * Don't start the thread, just do socket+bind+listen (Martin KaFai Lau) v2: * Update documentation (Andrey Ignatov) * Pass BIND_FORCE_ADDRESS_NO_PORT conditionally (Andrey Ignatov) Signed-off-by: Stanislav Fomichev <sdf@google.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Andrey Ignatov <rdna@fb.com> Acked-by: Martin KaFai Lau <kafai@fb.com> Link: https://lore.kernel.org/bpf/20200508174611.228805-5-sdf@google.com
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@ -1994,10 +1994,11 @@ union bpf_attr {
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*
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* This helper works for IPv4 and IPv6, TCP and UDP sockets. The
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* domain (*addr*\ **->sa_family**) must be **AF_INET** (or
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* **AF_INET6**). Looking for a free port to bind to can be
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* expensive, therefore binding to port is not permitted by the
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* helper: *addr*\ **->sin_port** (or **sin6_port**, respectively)
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* must be set to zero.
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* **AF_INET6**). It's advised to pass zero port (**sin_port**
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* or **sin6_port**) which triggers IP_BIND_ADDRESS_NO_PORT-like
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* behavior and lets the kernel efficiently pick up an unused
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* port as long as 4-tuple is unique. Passing non-zero port might
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* lead to degraded performance.
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* Return
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* 0 on success, or a negative error in case of failure.
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*
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