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bpf: Change bpf_sk_release and bpf_sk_*cgroup_id to accept ARG_PTR_TO_BTF_ID_SOCK_COMMON

The previous patch allows the networking bpf prog to use the bpf_skc_to_*() helpers to get a PTR_TO_BTF_ID socket pointer, e.g. "struct tcp_sock *". It allows the bpf prog to read all the fields of the tcp_sock. This patch changes the bpf_sk_release() and bpf_sk_*cgroup_id() to take ARG_PTR_TO_BTF_ID_SOCK_COMMON such that they will work with the pointer returned by the bpf_skc_to_*() helpers also. For example, the following will work: sk = bpf_skc_lookup_tcp(skb, tuple, tuplen, BPF_F_CURRENT_NETNS, 0); if (!sk) return; tp = bpf_skc_to_tcp_sock(sk); if (!tp) { bpf_sk_release(sk); return; } lsndtime = tp->lsndtime; /* Pass tp to bpf_sk_release() will also work */ bpf_sk_release(tp); Since PTR_TO_BTF_ID could be NULL, the helper taking ARG_PTR_TO_BTF_ID_SOCK_COMMON has to check for NULL at runtime. A btf_id of "struct sock" may not always mean a fullsock. Regardless the helper's running context may get a non-fullsock or not, considering fullsock check/handling is pretty cheap, it is better to keep the same verifier expectation on helper that takes ARG_PTR_TO_BTF_ID* will be able to handle the minisock situation. In the bpf_sk_*cgroup_id() case, it will try to get a fullsock by using sk_to_full_sk() as its skb variant bpf_sk"b"_*cgroup_id() has already been doing. bpf_sk_release can already handle minisock, so nothing special has to be done.

Martin KaFai Lau committed 6 years ago

Commit a5fa25a1 parent 1df8f553 files · +22 −24Browse files

Showing the changes to include/uapi (1 of 3 files). Show all

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include/uapi/linux/bpf.h+4−4
@@ -2512,7 +2512,7 @@ union bpf_attr { · 2511 unmodified lines
25122512 * result is from *reuse*\ **->socks**\ [] using the hash of the
25132513 * tuple.
25142514 *
2515− * long bpf_sk_release(struct bpf_sock *sock)
2515+ * long bpf_sk_release(void *sock)
25162516 * Description
25172517 * Release the reference held by *sock*. *sock* must be a
25182518 * non-**NULL** pointer that was returned from
@@ -3234,11 +3234,11 @@ union bpf_attr { · 715 unmodified lines
32343234 *
32353235 * **-EOVERFLOW** if an overflow happened: The same object will be tried again.
32363236 *
3237− * u64 bpf_sk_cgroup_id(struct bpf_sock *sk)
3237+ * u64 bpf_sk_cgroup_id(void *sk)
32383238 * Description
32393239 * Return the cgroup v2 id of the socket *sk*.
32403240 *
3241− * *sk* must be a non-**NULL** pointer to a full socket, e.g. one
3241+ * *sk* must be a non-**NULL** pointer to a socket, e.g. one
32423242 * returned from **bpf_sk_lookup_xxx**\ (),
32433243 * **bpf_sk_fullsock**\ (), etc. The format of returned id is
32443244 * same as in **bpf_skb_cgroup_id**\ ().
@@ -3248,7 +3248,7 @@ union bpf_attr { · 3 unmodified lines
32483248 * Return
32493249 * The id is returned or 0 in case the id could not be retrieved.
32503250 *
3251− * u64 bpf_sk_ancestor_cgroup_id(struct bpf_sock *sk, int ancestor_level)
3251+ * u64 bpf_sk_ancestor_cgroup_id(void *sk, int ancestor_level)
32523252 * Description
32533253 * Return id of cgroup v2 that is ancestor of cgroup associated
32543254 * with the *sk* at the *ancestor_level*. The root cgroup is at

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