Network Working Group A. Romanov Internet-Draft QQI Expires: September 23, 2002 March 25, 2002 Developing High Quality SNMP Agents draft-aromanov-snmp-hiqa-00 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on September 23, 2002. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract SNMP is a ubiquitous protocol. Most of the software developers working in the embedded space are involved into developing MIB handlers and SNMP agents one way or another. At the same time most of these developers are not directly involved into SNMP standard itself, and there is a number of often overlooked fine points there. This document will provide a list of steps and rules to avoid popular problems in order to develop a high quality SNMP agent. Romanov Expires September 23, 2002 [Page 1] Internet-Draft Developing High Quality SNMP Agents March 2002 Table of Contents 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 3. Index Processing Issues . . . . . . . . . . . . . . . . . . . 3 3.1 Index Process for Get and Set Requests . . . . . . . . . . . . 3 3.2 Index Process for GetNex and GetBulk Requests . . . . . . . . 4 4. Issues Related to the Set-Request Processing . . . . . . . . . 5 4.1 Consistency Checking . . . . . . . . . . . . . . . . . . . . . 5 4.2 Miscellaneous Set Request Issues . . . . . . . . . . . . . . . 6 5. Agent Design Issues . . . . . . . . . . . . . . . . . . . . . 7 6. Intellectual Propery . . . . . . . . . . . . . . . . . . . . . 8 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8 References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 9 A. GetNext and GetBulk Request Index Processing Examples . . . . 10 A.1 Processing Integer Index . . . . . . . . . . . . . . . . . . . 10 A.2 Processing IP Address Index . . . . . . . . . . . . . . . . . 11 A.3 Processing Non-implied String Index . . . . . . . . . . . . . 13 A.4 Putting It All Together . . . . . . . . . . . . . . . . . . . 17 Full Copyright Statement . . . . . . . . . . . . . . . . . . . 19 Romanov Expires September 23, 2002 [Page 2] Internet-Draft Developing High Quality SNMP Agents March 2002 1. Overview The goal of this memo is to facilitate development of SNMP agents in the context of SNMP agent framework. Modern SNMP agent frameworks are mature and they provide a good base to build a high-quality agent. These frameworks relieve an application developer from the bulk of the work related to the protocol transaction handling. However, there are still issues that have to be taken care of by an application developer. Unfortunately, there is a wide spread misunderstanding of some of the fine issues in this area. Moreover, there are new companies entering SNMP framework business, companies who develop their own frameworks and numerous companies that do deep modifications of existing frameworks. The author has an opportunity to observe it while working as a consultant for many years: even the most experienced developers usually miss/disregard one or more of the issues addressed in this memo. 2. Conventions Used in This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. 3. Index Processing Issues SNMP instance is identified by a string of OIDs representing the object name appended with a string of OIDs representing the index of the instance (we will call it an `index string'). In most cases it is left to the MIB developer to convert a string of index OIDs into application values e.g. integers, IP addresses, IP masks, and strings. 3.1 Index Process for Get and Set Requests Fortunately, there are very few problems arisen in this area. The first thing to do is to check the length of the index string and if it is inconsistent with the required length, `noSuchInstance' (`noCreation' if it is Set request) MUST be a result of the operation. Also, when the indexing by non-implied string (or non- implied object identifier) is used, the length of the string encoded as the first OID of the index string. This value MUST be checked against overall length of the index string too. Second, we have to remember that the range of OID (0-4294967295) is wider than the range of the variable it is being mapped into. For example, the range of integers used for index is 0-2147483647, the range of IP address components and the range of the string components is 0-255. So, OID 4123456789 indicates non-existent integer indexed Romanov Expires September 23, 2002 [Page 3] Internet-Draft Developing High Quality SNMP Agents March 2002 instance, index string 1.2.345.4 indicates non- existent instance indexed by IP address or IP mask and index string 4.65.66.670.68 indicates non-existent instance indexed by non- implied string. In all cases of incorrect range `noSuchInstance' (`noCreation') MUST be a result of the operation. So, index processing in the case is simple: check the length of the index string, check the range of every OID, and in case of any problems return `noSuchInstance' (`noCreation'). 3.2 Index Process for GetNex and GetBulk Requests Properly implemented SNMP agent does not expect that NMS would provide meaningful, properly formed and/or full index string. For example, in order to find the first remote host connected to particular local TCP port NM application would submit the GetNext- Request with partial index containing only local address and local port. Let us first spell out the general principles and then we will show how to apply them to the particular cases of various index specifications. It is worth to note here, that all known MIBs do have no more than one variable length index component and it is always the last one in the index string. So, in all practical cases starting offset of every index component is fixed within an index string. 1. If index string is longer than a properly formed one, it MUST be truncated. For example, if MIB variable is indexed by IP address, then the first instance after 1.2.3.4 and the first instance after 1.2.3.4.5.6.7.8 are the same instance. 2. If index string is shorter than the length of the properly formed one, (a) it MUST be padded with zeros and then (b) it MUST be checked whether there is an instance exactly matching padded index string. For example, if the MIB variable is indexed by IP address, then the first instance after 1.2.3 is 1.2.3.0 (if such instance exists). Skipping step (b) is a very popular bug. 3. If supplied index string contains out of range OID, then (a) if this OID is the first one in the index string search has to be advanced to the next object in the MIB view, otherwise (b) previous OID has to be incremented (if incrementing makes it out of range OID, then move to the previous OID and repeat steps (a) and (b)), (c) index string MUST be truncated starting from the OID, and then the operations of the step (2) above MUST be performed. Naturally, OID range checking MUST start at the end of index string and progress towards its beginning. Appendix A, contains index processing examples for the most popular cases. Romanov Expires September 23, 2002 [Page 4] Internet-Draft Developing High Quality SNMP Agents March 2002 4. Issues Related to the Set-Request Processing 4.1 Consistency Checking Unfortunately, there is a lot of confusion in the developer community with regard to the practical requirements of the depth and sophistication of consistency checking. Some developers assume that the standard requires that an agent should be able to verify consistency of every combination of variables that would fit into biggest Set-PDU. Naturally, they feel that this is an absolutely unrealistic requirement and they resort to completely ignore it. Others simply do best effort consistency checking with the actual meaning of the `best effort' that is varied wildly from product to product and even from MIB to MIB within the same product. Some companies build their own agent frameworks that impose severe restrictions on the ability of an agent to do effective consistency checking and some companies build agent frameworks that waste a lot of resources providing capabilities far beyond immediate necessity. And practically in all cases agent would not complain if it received Set-PDU that is more complicated than it is designed to process. Actually, the standard simply requires that (a) agent has to check consistency of every variable in the PDU vs. current managed device status and other variables in the PDU, (b) if variable is consistent and there is no `other' reasons preventing successful completion (e.g. if PDU has too many variables for a particular agent implementation to analyze) then set operation would continue, otherwise (c) `inconsistentValue' should be returned [RFC-PROTO]. So, what are the actual requirements on consistency checking abilities imposed by the standard? It is left to the developer, as in many other cases standard relies on the market place instead of specifying precise level. For example if a developer would aim too low, there will be problems with managing a device in the field and hence a considerable market place pressure to rectify the situation, if a developer would aim too high, it will negatively affect time to market and development costs. Does standard allow to implement SNMP agent accepting only one variable per Set-PDU? It is not prohibited by protocol operations [RFC-PROTO];however, all SNMP agents have to implement SNMP MIB [RFC- MIB]. This MIB contains a variable TestAndIncr [RFC2579] snmpSetSerialNo; TestAndIncr objects (often called spinlocks) are intended to control access to other objects, so they have to be present in the PDU together with the variables, which they control access to. So, it will impossible to fully implement even minimally required set of MIBs with the agent accepting only one variable per Set-PDU. Romanov Expires September 23, 2002 [Page 5] Internet-Draft Developing High Quality SNMP Agents March 2002 So, let us spell out the requirement for the "minimal" implementation of an SNMP agent: (a) an agent MUST be able to properly check consistency of the following combination of variables (regardless of order in the PDU): (1) snmpSetSerialNo, (2) any variable, (3) any combination of spin-lock variables associated with the above variable, if any; (b) agent MUST return `inconsistentValue' if the complexity of Set-PDU exceeds agents ability to perform consistency checking. Again, skipping requirement (b) is a very popular bug. Naturally, this implementation should use `createAndWait' method of row creation. Does implementing an agent with minimal level make much sense? In many cases it is a perfectly valid implementation, at the same time, it is very limiting for many practical cases. So, the "reasonable" implementation of an SNMP agent SHOULD support row creation with `createAndGo' and it SHOULD provide consistency checking extended at least to the variables belonging to a single row in the conceptual table. Reasonable implementation provides substantial benefits, with minimal additional efforts. Naturally, nothing prevents developer to go way beyond reasonable implementation level, let us call such implementations "advanced". Also, it is perfectly legal to mix various levels of implementation within the same agent. Developers who develop or customize SNMP agent frameworks have to be very careful with selecting maximum implementation level supported by the framework. For example, if framework supports only minimal implementation, it will be hardly possible to implement legacy MIBs with tables without RowStatus component. Also, there is an often-overlooked issue mostly related to the consistency checking in "advanced" implementations. There are always a number of managed systems parameters where consistency checking, resource allocation and/or undo operations are practically impossible to accomplish with 100% level of reliability. Good thing is that as a rule these operations are inherently atomic and the failure do not change the management system state. Consistency checking in the case SHOULD not allow these variables to be mixed with any other non spin- lock variable, so the dangerous operation would use on inherent atomicity instead of checking. 4.2 Miscellaneous Set Request Issues The intended use of `createAndWait' and `notInService' RowStatus values is to create and manipulate very long rows. Otherwise, they do not provide any additional value so reasonable and advanced implementations of an SNMP agent MAY NOT support these values for MIBs with rows of normal length. Naturally, minimal implementation Romanov Expires September 23, 2002 [Page 6] Internet-Draft Developing High Quality SNMP Agents March 2002 MUST support these values. The `commitFailed' error code does not convey any meaningful information to NMS, an SNMP agent MAY substitute some meaningful error code (e.g. `resourceNotAvailable') in the case. Naturally, an SNMP agent SHOULD NOT ever find itself in the situation where it will return `undoFailed'. 5. Agent Design Issues There are a number of design issues to be considered. It may require a separate memo to discuss each of them in detail. So, this memo will be limited to a brief listing of often overlooked design issues. 1. The spectrum and frequency of requests issued by NMSs are unpredictable and there is always a pretty real possibility of NMS bugs, which can result in the excessive load on the SNMP agent. So, it is essential to run SNMP agents as a low priority thread or to take other steps to prevent SNMP agent activities from affecting managed system performance. This is also a security issue, described below. 2. There is a popular design that links rows in the GetNext order and also puts them into a hash table to provide fast access to the current row. It works perfectly well for Get and Set operations and it also works fine the bulk of GetNext cases, when search string exactly matches an existing row. However, NMS has no responsibility to provide index of an existing instance as an index string, so in some cases long linear search is unavoidable. So it is important to take some precautions to guarantee that long linear search would not impact managed system performance (e.g. along the lines of item (1) above). 3. On the systems with memory protection, it is advisable to map tables into read-only shared memory, because user space-kernel space transitions are very expensive, so along the lines of the item (1) above kernel transactions should be limited only to the area where it is absolutely essential: namely set requests. 4. Often, it is desirable to provide a common backend for various management interfaces (SNMP, WEB, CORBA, CLI, etc.). It is surprisingly popular to select SNMP agent as such a backend. Author strongly advises against this design, unless the managed device is a truly trivial one. In author's experience it never brought to anybody anything but trouble. Romanov Expires September 23, 2002 [Page 7] Internet-Draft Developing High Quality SNMP Agents March 2002 6. Intellectual Propery The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in [RFC2028]. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. 7. Security Considerations SNMPv3 security specifically does not protect against denial of service attacks [SNMP-USM], so SNMPv3 entities are relatively vulnerable to these attacks: in most configurations NMSs make a substantial use of insecure communications to convey essential information, agent allows pretty significant replay window, which could be exploited to overload the managed system with requests. Using complex instance level granularity access greatly aggravates the situation. Also, SNMPv3 agent security configuration is a complex matter, even minor imperfection in the agent's security configuration may expose the managed system to the inappropriate level of the risk. So, it is RECOMMENDED to have a built-in possibility to start an agent in `high-security mode' where it will drop all insecure communications delivered to it and it will never emit an insecure communication on its own, regardless of its configuration parameters. Also, it is RECOMMENDED to strictly follow design recommendation (1) in the previous section in order to eliminate vulnerabilities associated with the denial of service attacks exploiting replay window. For the same purpose it is RECOMMENDED that agent would start any Set request with processing of the snmpSetSerialNo if it is present in the PDU. It is not related to the agent side, however, it Romanov Expires September 23, 2002 [Page 8] Internet-Draft Developing High Quality SNMP Agents March 2002 is important to rememeber that every NMS issuing a Set request without snmpSetSerialNo exposes an agent to a possible denial of service attack. References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC-PROTO] Rose, M., Case, J., Waldbusser, S., McCloghrie, K. and R. Presuhn, "Version 2 of the Protocol Operations for the Simple Network Management Protocol", draft-ietf- snmpv3-update-proto-08 (work in progress), October 2001. [RFC-MIB] Rose, M., Case, J., Waldbusser, S., McCloghrie, K. and R. Presuhn, "Management Information Base for the Simple Network Management Protocol", draft-ietf-snmpv3-update- mib-07 (work in progress), October 2001. [RFC2579] McCloghrie, K., Perkins, D., Schoenwaelder, J., Case, J., McCloghrie, K., Rose, M. and S. Waldbusser, "Textual Conventions for SMIv2", STD 58, RFC 2579, April 1999. [RFC2028] Hovey, R. and S. Bradner, "The Organizations Involved in the IETF Standards Process", BCP 11, RFC 2028, October 1996. [SNMP-USM] Wijnen, B. and U. Blumenthal, "User-based Security Model (USM) for version 3 of the Simple Network Management Protocol (SNMPv3)", draft-ietf-snmpv3-usm-v2-rfc2574bis- 01 (work in progress), November 2001. [RFC2012] McCloghrie, K., "SNMPv2 Management Information Base for the Transmission Control Protocol using SMIv2", RFC 2012, November 1996. Author's Address Aleksey Romanov Quality Quorum, Inc. 24 Highland View Dr. Sutton, MA 01590 US Phone: +1 508 865 3205 EMail: qqi@world.std.com Romanov Expires September 23, 2002 [Page 9] Internet-Draft Developing High Quality SNMP Agents March 2002 Appendix A. GetNext and GetBulk Request Index Processing Examples A.1 Processing Integer Index Below is a function that converts a part of an index string into integer. This function converts OID located at offset `off' in the fully formed index string, index string supplied by NMS is represented by `indexString' and `indexStringLength'. Note: `off' could be greater or equal than `indexStringLength'. If fully formed index string does not end with the integer in question, it is quite possible that processing of the next index component would require to increment current OID, in this case `inBump' will be non-zero. The maximum acceptable value is passed as `maxIntVal'. Converted integer will be placed into `intVal'. If exactly matching instance has to be probed first, `checkExact' will be set to non-zero value. This function returns non-zero value if the previous OID has to be incremented. int nextprocOid2Int(const uint32 *indexString, int indexStringLength, int off, int inBump, int32 maxIntVal, int32 *intVal, int *checkExact) { uint32 oidVal; assert(indexString != NULL || indexStringLength == 0); assert(indexStringLength >= 0); assert(off >= 0); assert(indexStringLength > (off+1) || !inBump); assert(maxIntVal >= 0); assert(intVal != NULL); assert(checkExact != NULL); if(off >= indexStringLength) { /* Index string is short */ assert(inBump == 0); *intVal = 0; *checkExact = 1; return 0; } oidVal = indexString[off]; if(oidVal > (uint32)maxIntVal || Romanov Expires September 23, 2002 [Page 10] Internet-Draft Developing High Quality SNMP Agents March 2002 (inBump && oidVal == (uint32)maxIntVal)) { /* OID is out of range */ *intVal = 0; *checkExact = 1; return 1; } if(inBump) { *intVal = oidVal + 1; } else { *intVal = oidVal; } *checkExact = 0; return 0; } A.2 Processing IP Address Index Below is a function that converts a part of an index string into IP address. This function converts OIDs started at offset `off' in the fully formed index string, index string supplied by NMS is represented by `indexString' and `indexStringLength'. Note `off' could be greater or equal than 'indexStringLength'. If fully formed index string does not end with the IP address in question, it is quite possible that processing of the next index component would require to increment the last OID of current component, in this case `inBump' will be non-zero. Converted IP address (in host order) will be placed into `addrVal'. If exact matching instance has to be probed first, `checkExact' will be set to non-zero value. This function returns non-zero value if the previous OID has to be incremented. int nextprocOid2IpAddr(const uint32 *indexString, int indexStringLength, int off, int inBump, uint32 *addrVal, int *checkExact) { const uint32 *oid, *first, *last; Romanov Expires September 23, 2002 [Page 11] Internet-Draft Developing High Quality SNMP Agents March 2002 uint32 tmp; int exact; assert(indexString != NULL || indexStringLength == 0); assert(indexStringLength >= 0); assert(off >= 0); assert(indexStringLength > (off + 5) || !inBump); assert(intVal != NULL); assert(checkExact != NULL); if(off >= indexStringLength) { /* Index string is short */ assert(inBump == 0); *addrVal = 0; *checkExact = 1; return 0; } first = &indexString[off]; exact = 0; if(indexStgringLength >= (off + 4)) { /* We have full address specified */ last = &indexString[off+3]; } else { last = &indexString[indexStringLength-1]; exact = 1; } tmp = 0; for(oid=last; oid>=first; oid--) { if(*oid > 255 || (inBump && *oid == 255)) { if(oid == first) { *addrVal = 0; *checkExact = 1; return 1; } Romanov Expires September 23, 2002 [Page 12] Internet-Draft Developing High Quality SNMP Agents March 2002 tmp = 0; exact = 1; inBump = 1; continue; } if(inBump) { tmp += (((*oid) + 1) << 8*(3 - (oid - first))); inBump = 0; } else { tmp += ((*oid) << 8*(3 - (oid - first))); } } assert(!inBump); *addrVal = tmp; *checkExact = exact; return 0; } A.3 Processing Non-implied String Index First it may worth reminding that the first element of this index is the length of the string, so "bb" would go before "aaa", which may be counterintuitive for developers accustomed to normal C-string ordering. Below is a function that converts a part of an index string into array of unsigned characters. This function converts OIDs started at offset `off' in the fully formed index string, index string supplied by NMS is represented by `indexString' and `indexStringLength'. Note: `off' can be greater or equal than `indexStringLength'. In all practical cases this element will be the last one in the index string, so we are not going to be too generic and this function does not include `inBump' parameter. Converted string will be placed into `stringVal', the length of available buffer is passed as `maxStringLength', and the length of processed string is placed into `stringLength'. If exact matching instance has to be probed first, `checkExact' has to be set to non-zero value. This function returns Romanov Expires September 23, 2002 [Page 13] Internet-Draft Developing High Quality SNMP Agents March 2002 non-zero value if the previous OID has to be incremented. int nextprocOid2Str(const uint32 *indexString, int indexStringLength, int off, int maxStringLength, int *stringLength, uint8* stringVal, int *checkExact) { const uint32 *oid, *first, *last; int len, bump; uint8 *s, *resetStart; assert(indexString != NULL || indexStringLength == 0); assert(indexStringLength >= 0); assert(off >= 0); assert(maxStringLength > 0); assert(stringLength != NULL); assert(stringVal != NULL); assert(checkExact != NULL); if(off >= indexStringLength) { /* Index string is short */ *stringLength = 0; *checkExact = 1; return 0; } if(maxStringLength > 128) { /* There is no point to deal with strings longer, than the whole name length limit, imposed by protocol */ maxStringLength = 128; } if(indexStgring[off] > (uint32)maxStringLength) { *stringLength = 0; *checkExact = 1; return 1; } len = (int)indexString[off]; Romanov Expires September 23, 2002 [Page 14] Internet-Draft Developing High Quality SNMP Agents March 2002 if(len == 0) { /* Empty string */ *stringLength = 0; *checkExact = 0; return 0; } off++; if(off >= indexStringLength) { /* Only length is present */ memset(stringVal, 0, len); *stringLength = len; *checkExact = 1; return 0; } first = &indexString[off]; if(indexStgringLength >= (off + len)) { /* We have full string provided */ last = &indexString[off+len-1]; resetStart = NULL; } else { last = &indexString[indexStringLength-1]; resetStart = stringVal + (indexStringLength - off); } bump = 0; for(oid=last,s=stringVal+(last - first); oid>=first; oid--,s--) { assert((s - stringVal) == (oid - first)); if(*oid > 255 || (bump && *oid == 255)) { resetStart = s; bump = 1; continue; } Romanov Expires September 23, 2002 [Page 15] Internet-Draft Developing High Quality SNMP Agents March 2002 if(bump) { *s = (uint8) ((*oid) + 1); bump = 0; } else { *s += (uint8)(*oid); } } if(bump) { if(len == maxStringLength) { *stringLength = 0; *checkExact = 1; return 1; } len++; memset(stringVal, 0, len); *stringLength = len; *checkExact = 1; return 0; } *stringLength = len; if(resetStart != NULL) { assert((resetStart - stringVal) < len); memset(resetStart, 0, (len - (resetStart - stringVal))); *checkExact = 1; } else { *checkExact = 0; } return 0; } Romanov Expires September 23, 2002 [Page 16] Internet-Draft Developing High Quality SNMP Agents March 2002 A.4 Putting It All Together Let us consider an example of tcpConnTable, it is indexed by tcpConnLocalAddress, tcpConnLocalPort, tcpConnRemAddress and tcpConnRemPort where the corresponding index string offsets are 0, 4, 6, and 10 [RFC2012] int nextTcpTableEntry(const uint32 indexString, int indexStringLength, struct tcpTableEntry *e) { int ret, bump, exact, curExact; int32 localPort, remotePort; uint32 localAddr, remoteAddr; exact = 0; bump = nextprocOid2Int(indexString, indexStringLength, 10, 0, 0xffff, &remotePort, &curExact); if(curExact) { exact = 1; } bump = nextprocOid2IpAddr(indexString, indexStringLength, 6, bump, &remoteAddr, &curExact); if(curExact) { exact = 1; remotePort = 0; } bump = nextprocOid2Int(indexString, indexStringLength, 4, bump, 0xffff, &localPort, &curExact); if(curExact) { exact = 1; remotePort = 0; remoteAddr = 0; Romanov Expires September 23, 2002 [Page 17] Internet-Draft Developing High Quality SNMP Agents March 2002 } bump = nextprocOid2IpAddr(indexString, indexStringLength, 0, bump, &localAddr, &curExact); if(bump) { return NOTFOUND; } if(curExact) { exact = 1; remotePort = 0; remoteAddr = 0; localPort = 0; } ret = NOTFOUND; if(exact) { ret = retriveTcpConnection(localAddr, localPort, remoteAddr, remotePort, e); } if(ret == NOTFOUND) { ret = retrieveNextTcpConnection(localAddr, localPort, remoteAddr, remotePort, e); } return ret; } Romanov Expires September 23, 2002 [Page 18] Internet-Draft Developing High Quality SNMP Agents March 2002 Full Copyright Statement Copyright (C) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Romanov Expires September 23, 2002 [Page 19]