Squash to "selftests/bpf: Add getsockopt to inspect mptcp subflow"

Update error messages:

 run_subflow:FAIL:mark unexpected mark: actual 3 != expected 0
 run_subflow:FAIL:cc unexpected cc: actual 'reno' != expected 'cubic'

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>

tools/testing/selftests/bpf/progs/mptcp_subflow.c

@@ -63,6 +63,7 @@ int mptcp_subflow(struct bpf_sock_ops *skops)
 static int _check_getsockopt_subflow_mark(struct mptcp_sock *msk, struct bpf_sockopt *ctx)
 {
  struct mptcp_subflow_context *subflow;
+ int *optval = ctx->optval;
  int i = 0;
 
  mptcp_for_each_subflow(msk, subflow) {
@@ -72,7 +73,10 @@ static int _check_getsockopt_subflow_mark(struct mptcp_sock *msk, struct bpf_soc
  struct mptcp_subflow_context));
 
  if (ssk->sk_mark != ++i) {
- ctx->retval = -2;
+ if (ctx->optval + sizeof(int) <= ctx->optval_end) {
+ *optval = ssk->sk_mark;
+ ctx->retval = 0;
+ }
  break;
  }
  }
@@ -83,6 +87,7 @@ static int _check_getsockopt_subflow_mark(struct mptcp_sock *msk, struct bpf_soc
 static int _check_getsockopt_subflow_cc(struct mptcp_sock *msk, struct bpf_sockopt *ctx)
 {
  struct mptcp_subflow_context *subflow;
+ char *optval = ctx->optval;
 
  mptcp_for_each_subflow(msk, subflow) {
  struct inet_connection_sock *icsk;
@@ -94,7 +99,10 @@ static int _check_getsockopt_subflow_cc(struct mptcp_sock *msk, struct bpf_socko
 
  if (ssk->sk_mark == 2 &&
  __builtin_memcmp(icsk->icsk_ca_ops->name, cc, TCP_CA_NAME_MAX)) {
- ctx->retval = -2;
+ if (ctx->optval + TCP_CA_NAME_MAX <= ctx->optval_end) {
+ __builtin_memcpy(optval, icsk->icsk_ca_ops->name, TCP_CA_NAME_MAX);
+ ctx->retval = 0;
+ }
  break;
  }
  }