On 4/29/20 7:05 PM, Stanislav Fomichev wrote:
Currently, bpf_getsocktop and bpf_setsockopt helpers operate on the
'struct bpf_sock_ops' context in BPF_PROG_TYPE_SOCK_OPS program.
Let's generalize them and make the first argument be 'struct bpf_sock'.
That way, in the future, we can allow those helpers in more places.
BPF_PROG_TYPE_SOCK_OPS still has the existing helpers that operate
on 'struct bpf_sock_ops', but we add new bpf_{g,s}etsockopt that work
on 'struct bpf_sock'. [Alternatively, for BPF_PROG_TYPE_SOCK_OPS,
we can enable them both and teach verifier to pick the right one
based on the context (bpf_sock_ops vs bpf_sock).]
As an example, let's allow those 'struct bpf_sock' based helpers to
be called from the BPF_CGROUP_INET{4,6}_CONNECT hooks. That way
we can override CC before the connection is made.
v2:
* s/BPF_PROG_TYPE_CGROUP_SOCKOPT/BPF_PROG_TYPE_SOCK_OPS/
Acked-by: John Fastabend <john.fastabend@xxxxxxxxx>
Acked-by: Martin KaFai Lau <kafai@xxxxxx>
Signed-off-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
[...]
+BPF_CALL_5(bpf_setsockopt, struct sock *, sk,
+ int, level, int, optname, char *, optval, int, optlen)
+{
+ u32 flags = 0;
+ return _bpf_setsockopt(sk, level, optname, optval, optlen, flags);
+}
+
+static const struct bpf_func_proto bpf_setsockopt_proto = {
+ .func = bpf_setsockopt,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_SOCKET,
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_ANYTHING,
+ .arg4_type = ARG_PTR_TO_MEM,
+ .arg5_type = ARG_CONST_SIZE,
+};
+
+BPF_CALL_5(bpf_getsockopt, struct sock *, sk,
+ int, level, int, optname, char *, optval, int, optlen)
+{
+ return _bpf_getsockopt(sk, level, optname, optval, optlen);
+}
+
static const struct bpf_func_proto bpf_getsockopt_proto = {
.func = bpf_getsockopt,
.gpl_only = false,
.ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_SOCKET,
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_ANYTHING,
+ .arg4_type = ARG_PTR_TO_UNINIT_MEM,
+ .arg5_type = ARG_CONST_SIZE,
+};
+
[...]
@@ -6043,6 +6098,22 @@ sock_addr_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_sk_storage_get_proto;
case BPF_FUNC_sk_storage_delete:
return &bpf_sk_storage_delete_proto;
+ case BPF_FUNC_setsockopt:
+ switch (prog->expected_attach_type) {
+ case BPF_CGROUP_INET4_CONNECT:
+ case BPF_CGROUP_INET6_CONNECT:
+ return &bpf_setsockopt_proto;
Hm, I'm not sure this is safe. In the sock_addr_func_proto() we also have
other helpers callable from connect hooks like sk_lookup_{tcp,udp} which
return a PTR_TO_SOCKET_OR_NULL, and now we can pass those sockets also into
bpf_{get,set}sockopt() helper after lookup to change various sk related stuff
but w/o being under lock. Doesn't the sock_owned_by_me() yell here at minimum
(I'd expect so)?
+ default:
+ return NULL;
+ }
+ case BPF_FUNC_getsockopt:
+ switch (prog->expected_attach_type) {
+ case BPF_CGROUP_INET4_CONNECT:
+ case BPF_CGROUP_INET6_CONNECT:
+ return &bpf_getsockopt_proto;
+ default:
+ return NULL;
+ }
default:
