bpf: Move the "cdg" tcp-cc check to the common sol_tcp_sockopt()

The check on the tcp-cc, "cdg", is done in the bpf_sk_setsockopt which is
used by the bpf_tcp_ca, bpf_lsm, cg_sockopt, and tcp_iter hooks.
However, it is not done for cg sock_ddr, cg sockops, and some of
the bpf_lsm_cgroup hooks.

The tcp-cc "cdg" should have very limited usage.  This patch is to
move the "cdg" check to the common sol_tcp_sockopt() so that all
hooks have a consistent behavior.   The motivation to make
this check consistent now is because the latter patch will
refactor the bpf_setsockopt(TCP_CONGESTION) into another function,
so it is better to take this chance to refactor this piece
also.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20220929070407.965581-3-martin.lau@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/net/core/filter.c b/net/core/filter.c
index 2fd9449..f4cea3f 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5127,6 +5127,13 @@ static int sol_tcp_sockopt(struct sock *sk, int optname,
        case TCP_CONGESTION:
                if (*optlen < 2)
                        return -EINVAL;
+               /* "cdg" is the only cc that alloc a ptr
+                * in inet_csk_ca area.  The bpf-tcp-cc may
+                * overwrite this ptr after switching to cdg.
+                */
+               if (!getopt && *optlen >= sizeof("cdg") - 1 &&
+                   !strncmp("cdg", optval, *optlen))
+                       return -ENOTSUPP;
                break;
        case TCP_SAVED_SYN:
                if (*optlen < 1)
@@ -5285,12 +5292,6 @@ static int _bpf_getsockopt(struct sock *sk, int level, int optname,
 BPF_CALL_5(bpf_sk_setsockopt, struct sock *, sk, int, level,
           int, optname, char *, optval, int, optlen)
 {
-       if (level == SOL_TCP && optname == TCP_CONGESTION) {
-               if (optlen >= sizeof("cdg") - 1 &&
-                   !strncmp("cdg", optval, optlen))
-                       return -ENOTSUPP;
-       }
-
        return _bpf_setsockopt(sk, level, optname, optval, optlen);
 }