Some function tests returned error

[jijianwen]

Commit eaf7032 fixed the compilation error. My system is rhel-7.5 which has /usr/include/linux/sctp.h，but when compiling lksctp-tools, it uses src/include/linux/sctp.h as default. After compilation, I got some error when executing test programs under func_tests directory. The reason should be that some structures are different between 2 header files. For example:
setsockopt(SCTP_EVENTS) in test_1_to_1_events returned Invalid arguments.

I think kernel checked the size of relevant struct and returned error for there are more fields in src/include/linux/sctp.h than /usr/include/linux/sctp.h

[marceloleitner]

Your reasoning is correct. This exhibits a backward compatibility issue that was already there: newer lksctp-tools, with updated structs, also wouldn't work with kernels not having those fields in struct sctp_event_subscribe.

[marceloleitner]

We should fix this at kernel level, with something like:

--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -2320,7 +2320,7 @@ static int sctp_setsockopt_events(struct sock *sk, char __user *optval,
        struct sctp_ulpevent *event;

        if (optlen > sizeof(struct sctp_event_subscribe))
-               return -EINVAL;
+               optlen = sizeof(struct sctp_event_subscribe);
        if (copy_from_user(&sctp_sk(sk)->subscribe, optval, optlen))
                return -EFAULT;

@@ -2342,7 +2342,7 @@ static int sctp_setsockopt_events(struct sock *sk, char __user *optval,
                }
        }

-       return 0;
+       return optlen;
 }

 /* 7.1.8 Automatic Close of associations (SCTP_AUTOCLOSE)

Still need to check for other possible occurrences of similar issues.

[marceloleitner]

Scratch my previous comment. The issue is that the local copy is always being used, even where it should be using the system UAPI one. I fixed issue #22 and issue #23 wrongly. Instead, the library needs to probe what the kernel supports while building and only use that.
I'll use this issue to fix all this.