: Convert Reset code into socket error number

Please find below reworked version of patch to match coding style and to use a sentinel member as per Ian's suggestion (many thanks).

----------------------------> Patch v2 <----------------------------------------------------------- [DCCP]: Convert Reset code into socket error number

This adds support for converting the 11 currently defined Reset codes into system error numbers, which are stored in sk_err for further interpretation.

This makes the externally visible API behaviour similar to TCP, since a client connecting to a non-existing port will experience ECONNREFUSED.

* Code 0, Unspecified, is interpreted as non-error (0);
* Code 1, Closed (normal termination), also maps into 0;
* Code 2, Aborted, maps into "Connection reset by peer" (ECONNRESET);
* Code 3, No Connection and
Code 7, Connection Refused, map into "Connection refused" (ECONNREFUSED);
* Code 4, Packet Error, maps into "No message of desired type" (ENOMSG);
* Code 5, Option Error, maps into "Illegal byte sequence" (EILSEQ);
* Code 6, Mandatory Error, maps into "Operation not supported on transport endpoint" (EOPNOTSUPP);
* Code 8, Bad Service Code, maps into "Invalid request code" (EBADRQC);
* Code 9, Too Busy, maps into "Too many users" (EUSERS);
* Code 10, Bad Init Cookie, maps into "Invalid request descriptor" (EBADR);
* Code 11, Aggression Penalty, maps into "Quota exceeded" (EDQUOT)
which makes sense in terms of using more than the `fair share' of bandwidth.

---
 include/linux/dccp.h |    2 ++
 net/dccp/input.c     |   48 +++++++++++++++++++++++++++++++++++++++---------
 2 files changed, 41 insertions(+), 9 deletions(-)

@@ -146,6 +146,8 @@ enum dccp_reset_codes {
 	DCCP_RESET_CODE_TOO_BUSY,
 	DCCP_RESET_CODE_BAD_INIT_COOKIE,
 	DCCP_RESET_CODE_AGGRESSION_PENALTY,
+
+	DCCP_MAX_RESET_CODES		/* Leave at the end!  */
 };
 
 /* DCCP options */