RFR: 8267938: SCTP channel factory methods should check platform support

[Chris Hegarty]

The SCTP channel factory methods, namely SctpChannel::open, SctpServerChannel::open, and SctpMultiChannel::open, are specified to throw UnsupportedOperationException, if the SCTP protocol is not supported. Currently, underlying platform support is assumed once the appropriate libsctp.so.1 library is present (along with its supported interface functions). This may not always be the case, e.g. if the Linux sctp kernel module is not present or loaded. In which case a SocketException is thrown.

It would be more appropriate to check for EPROTONOSUPPORT and ESOCKTNOSUPPORT, and throw UOE rather than SE.

The existing java/net/SctpSanity.java tests already covers this case, when run on platforms without support.

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Commit messages:
 - Initial changes

Changes: https://git.openjdk.java.net/jdk/pull/4246/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4246&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8267938
  Stats: 8 lines in 1 file changed: 6 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4246.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4246/head:pull/4246

PR: https://git.openjdk.java.net/jdk/pull/4246