[PATCH bpf-next] selftests/bpf: Fix compile error when MPTCP not support

[Tao Chen]

Fix compile error when MPTCP feature not support, though eBPF core check
already done which seems invalid in this situation, the error info like:
progs/mptcp_sock.c:49:40: error: no member named 'is_mptcp' in 'struct
tcp_sock'
   49 |         is_mptcp = bpf_core_field_exists(tsk->is_mptcp) ?

The filed created in new definitions with eBPF core feature to solve
this build problem, and test case result still ok in MPTCP kernel.

176/1   mptcp/base:OK
176/2   mptcp/mptcpify:OK
176     mptcp:OK
Summary: 1/2 PASSED, 0 SKIPPED, 0 FAILED

Fixes: 8039d353217c ("selftests/bpf: Add MPTCP test base")
Signed-off-by: Tao Chen <chen.dyl...@gmail.com>
---
 .../testing/selftests/bpf/progs/mptcp_sock.c  | 42 ++++++++++++++-----
 1 file changed, 32 insertions(+), 10 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/mptcp_sock.c 
b/tools/testing/selftests/bpf/progs/mptcp_sock.c
index f3acb90588c7..2f80d042686a 100644
--- a/tools/testing/selftests/bpf/progs/mptcp_sock.c
+++ b/tools/testing/selftests/bpf/progs/mptcp_sock.c
@@ -25,13 +25,23 @@ struct {
        __type(value, struct mptcp_storage);
 } socket_storage_map SEC(".maps");
 
+struct tcp_sock___new {
+       bool is_mptcp;
+} __attribute__((preserve_access_index));
+
+struct mptcp_sock___new {
+       __u32 token;
+       struct sock *first;
+       char ca_name[TCP_CA_NAME_MAX];
+} __attribute__((preserve_access_index));
+
 SEC("sockops")
 int _sockops(struct bpf_sock_ops *ctx)
 {
        struct mptcp_storage *storage;
-       struct mptcp_sock *msk;
+       struct mptcp_sock___new *msk;
        int op = (int)ctx->op;
-       struct tcp_sock *tsk;
+       struct tcp_sock___new *tsk;
        struct bpf_sock *sk;
        bool is_mptcp;
 
@@ -42,11 +52,16 @@ int _sockops(struct bpf_sock_ops *ctx)
        if (!sk)
                return 1;
 
-       tsk = bpf_skc_to_tcp_sock(sk);
+       /* recast pointer to capture new type for compiler */
+       tsk = (void *)bpf_skc_to_tcp_sock(sk);
        if (!tsk)
                return 1;
 
-       is_mptcp = bpf_core_field_exists(tsk->is_mptcp) ? tsk->is_mptcp : 0;
+       if (bpf_core_field_exists(tsk->is_mptcp))
+               is_mptcp = BPF_CORE_READ(tsk, is_mptcp);
+       else
+               is_mptcp = 0;
+
        if (!is_mptcp) {
                storage = bpf_sk_storage_get(&socket_storage_map, sk, 0,
                                             BPF_SK_STORAGE_GET_F_CREATE);
@@ -57,7 +72,7 @@ int _sockops(struct bpf_sock_ops *ctx)
                __builtin_memset(storage->ca_name, 0, TCP_CA_NAME_MAX);
                storage->first = NULL;
        } else {
-               msk = bpf_skc_to_mptcp_sock(sk);
+               msk = (void *)bpf_skc_to_mptcp_sock(sk);
                if (!msk)
                        return 1;
 
@@ -66,9 +81,9 @@ int _sockops(struct bpf_sock_ops *ctx)
                if (!storage)
                        return 1;
 
-               storage->token = msk->token;
-               __builtin_memcpy(storage->ca_name, msk->ca_name, 
TCP_CA_NAME_MAX);
-               storage->first = msk->first;
+               storage->token = BPF_CORE_READ(msk, token);
+               BPF_CORE_READ_STR_INTO(&storage->ca_name, msk, ca_name);
+               storage->first = BPF_CORE_READ(msk, first);
        }
        storage->invoked++;
        storage->is_mptcp = is_mptcp;
@@ -81,8 +96,15 @@ SEC("fentry/mptcp_pm_new_connection")
 int BPF_PROG(trace_mptcp_pm_new_connection, struct mptcp_sock *msk,
             const struct sock *ssk, int server_side)
 {
-       if (!server_side)
-               token = msk->token;
+       struct mptcp_sock___new *mskw;
+
+       if (!server_side) {
+               mskw = (void *)msk;
+               if (bpf_core_field_exists(mskw->token))
+                       token = BPF_CORE_READ(mskw, token);
+               else
+                       token = 0;
+       }
 
        return 0;
 }
-- 
2.43.0