On 4/30/20 4:24 AM, Alexei Starovoitov wrote:
On Wed, Apr 29, 2020 at 04:33:12PM -0700, sdf@xxxxxxxxxx wrote:On 04/30, Daniel Borkmann wrote: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)?Ugh, good point, I missed the fact that sk_lookup_{tcp,udp} are there for sock_addr :-( I can try to do a simple test case to verify that sock_owned_by_me triggers, but I'm pretty certain it should (I've been calling bpf_{s,g}etsockopt for context socket so it's quiet). I don't think there is any helper similar to sock_owned_by_me() that I can call to verify that the socket is held by current thread (without the lockdep splat) and bail out? In this case, is something like adding new PTR_TO_LOCKED_SOCKET_OR_NULL is the way to go? Any other ideas?Looks like networking will benefit from sleepable progs too. We could have just did lock_sock() inside bpf_setsockopt before setting cong control. In the mean time how about introducing try_lock_sock() that will bail out if it cannot grab the lock? For most practical cases that would work and eventually we can convert it to full lock_sock ?
Right, also, worst case we could also go back to having ctx as input arg. Thanks, Daniel
