projects / apple / security.git / blame
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1 | (RCS control information is at the end of this file.) |
| 2 | ||
| 3 | ||
| 4 | C SNMP Example - Mike Sample Mar 92 | |
| 5 | ----------------------------------- | |
| 6 | ||
| 7 | This example illustrates a few more features of the compiler than the | |
| 8 | simple example. It also shows some deficiencies. No executable | |
| 9 | programs are generated by the makefile, it only generates the snmp | |
| 10 | code and compiles it without linking. | |
| 11 | ||
| 12 | This directory contains 2 files: | |
| 13 | README | |
| 14 | makefile | |
| 15 | ||
| 16 | Snacc generates source from the following ASN.1 files: | |
| 17 | snacc/asn1specs/rfc1155_smi.asn1 | |
| 18 | snacc/asn1specs/rfc1157_snmp.asn1 | |
| 19 | snacc/asn1specs/rfc1213_mib2.asn1 | |
| 20 | ||
| 21 | multi-module compilation | |
| 22 | The IMPORT/EXPORT mechanisms of ASN.1 '88 are supported so you don't | |
| 23 | have to dump all of the ASN.1 definitions into a single file | |
| 24 | The order of the ASN.1 file arguments is the order that they | |
| 25 | are included in the generated source files. For example: | |
| 26 | ||
| 27 | %1 snacc rfc1155-smi.asn1 rfc1157-snmp.asn1 rfc1213-mib2.asn1 | |
| 28 | ||
| 29 | causes the order in which hdr files are included in rfc1213-mib.c | |
| 30 | to be: | |
| 31 | ||
| 32 | #include "asn-incl.h" | |
| 33 | #include "rfc1155-smi.h" | |
| 34 | #include "rfc1157-snmp.h" | |
| 35 | #include "rfc1213-mib2.h" | |
| 36 | ||
| 37 | ||
| 38 | Currently, snacc assumes that each ASN.1 file given on the command | |
| 39 | line depends on all of the others on the command line. There is | |
| 40 | no attempt to compute the dependencies via the import lists alone. | |
| 41 | ||
| 42 | SNMP OBJECT-TYPE macro parsing / ANY type hash table | |
| 43 | The SNMP OBJECT-TYPE macro is parsed. This results in the | |
| 44 | type in the "SYNTAX" part of the macro is put into | |
| 45 | the ANY type hash table using the OBJECT-TYPE macro's value as the | |
| 46 | hash key. Also if the type in the SYNTAX field is not defined | |
| 47 | outsided of the macro (could be different tagging etc), a proper | |
| 48 | type definition is generated for it. If you want to change the way | |
| 49 | the macro is handled, modify the corresponding routine in "do_macros.c". | |
| 50 | ||
| 51 | value definitions | |
| 52 | The OBJECT IDENTIFIER values are turned into statically initialized | |
| 53 | C values and included in the generated source and include file. This | |
| 54 | is also done for INTEGER and BOOLEAN values. More complex values | |
| 55 | are ignored by the compiler at the moment. (modify parse_vals.c if | |
| 56 | you want to improve this) | |
| 57 | ||
| 58 | ||
| 59 | -P option of snacc is demonstrated | |
| 60 | The ASN.1 for the parsed modules is generated from the internal data | |
| 61 | structure. This can be useful for making sure the compiler is | |
| 62 | handling your ASN.1 files correctly. It is also useful to see how | |
| 63 | the types are modified and sorted to simplify code generation. | |
| 64 | (see the snacc.output file after typeing "make") | |
| 65 | ||
| 66 | Deficiencies | |
| 67 | A deficiency in parsing large integers is shown when parsing the | |
| 68 | following rfc 1155 types: | |
| 69 | ||
| 70 | Counter ::= | |
| 71 | [APPLICATION 1] | |
| 72 | IMPLICIT INTEGER (0..4294967295) | |
| 73 | ||
| 74 | Gauge ::= | |
| 75 | [APPLICATION 2] | |
| 76 | IMPLICIT INTEGER (0..4294967295) | |
| 77 | ||
| 78 | TimeTicks ::= | |
| 79 | [APPLICATION 3] | |
| 80 | IMPLICIT INTEGER (0..4294967295) | |
| 81 | ||
| 82 | Due the size of a C long int the above ASN.1 is represented internally as: | |
| 83 | ||
| 84 | Counter ::= [APPLICATION 1] IMPLICIT INTEGER (0..-1) | |
| 85 | ||
| 86 | Gauge ::= [APPLICATION 2] IMPLICIT INTEGER (0..-1) | |
| 87 | ||
| 88 | TimeTicks ::= [APPLICATION 3] IMPLICIT INTEGER (0..-1) | |
| 89 | ||
| 90 | The ASN.1 library contains routines for encoding/decoding unsigned | |
| 91 | long integers but you must hand code the cases where it is used - the | |
| 92 | compiler never generates code that calls them. | |
| 93 | ||
| 94 | Note also that the produced code for the SNMP ASN.1 must be modified | |
| 95 | to correclty handle the "Opaque" data type. SNMP does not use the ANY | |
| 96 | DEFINED BY type in an effort to simplify things. Instead an OCTET | |
| 97 | STRING is used to hold and encoded value whose type is defined by an | |
| 98 | OBJECT IDENTIFIER. With some simple modifications you can use the | |
| 99 | snacc AsnAnyDefinedBy type instead of the OCTET STRING to achieve | |
| 100 | the desired results. | |
| 101 | ||
| 102 | This should underline the danger of blindly trusting the compiler to | |
| 103 | do the right thing for protocols such as SNMP or X.500 where the type | |
| 104 | of an encoded value depends on a mechanism outside of ASN.1 or the ANY | |
| 105 | type (ANY DEFINED BY types should work automatically). | |
| 106 | ||
| 107 | #------------------------------------------------------------------------------- | |
| a66d0d4a | 108 | # $Header: /cvs/root/Security/SecuritySNACCRuntime/c-examples/snmp/Attic/README,v 1.1.1.1 2001/05/18 23:14:07 mb Exp $ |
| bac41a7b A |
109 | # $Log: README,v $ |
| 110 | # Revision 1.1.1.1 2001/05/18 23:14:07 mb | |
| 111 | # Move from private repository to open source repository | |
| 112 | # | |
| 113 | # Revision 1.1.1.1 1999/03/16 18:06:09 aram | |
| 114 | # Originals from SMIME Free Library. | |
| 115 | # | |
| 116 | # Revision 1.3 1995/07/27 09:58:31 rj | |
| 117 | # rfc1155-smi.asn1, rfc1157-snmp.asn1 and rfc1213-mib2.asn1 renamed from 1155-smi.asn1, 1157-snmp.asn1 and 1213-mib2.asn1 to accomodate to snacc's new file name generation scheme. | |
| 118 | # | |
| 119 | # Revision 1.2 1995/07/24 20:47:39 rj | |
| 120 | # changed `_' to `-' in file names. | |
| 121 | # | |
| 122 | # Revision 1.1 1994/08/31 08:46:33 rj | |
| 123 | # first check-in. for a list of changes to the snacc-1.1 distribution please refer to the ChangeLog. | |
| 124 | # |