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    <h1>rstory's NET-SNMP Developers Frequently Asked Questions Page</h1>
    </div>
<hr>
    <div align=center>
    <font size=-1>
      <a href="FAQ.html">[Official FAQ]</a> | 
	<a href="#tokens">[Debug tokens]</a> | 
	<a href="#agentx">[AgentX]</a> | 
	<a href="#install">[Install]</a> | 
	<a href="#disable">[Disable]</a> | 
	<a href="#errors">[Errors]</a> | 
	<a href="#bits">[Bits]</a> | 
	<a href="#embedded">[embedded perl]</a> | 
	<a href="#smux">[SMUX]</a> | 
	<a href="#entid">[Enterprise OID]</a> | 
	<a href="#autodeps">[Automatic dependencies]</a> | 
	<a href="#cross">[Cross compiling]</a> | 
	<a href="#static">[Static linking]</a> | 
	<a href="#readfds">[readfds]</a> | 
	<a href="#sharing">[Sharing data]</a> | 
	<a href="man1-mib2c.1.html">[mib2c.array-user.conf]</a> | 
	<a href="#steps">[Baby Steps flow]</a> | 
      </font>
    </div>
<hr>
This is just a quick page to answer some common questions that aren't covered
in the <a href="/FAQ.html">official FAQ</a>.

<a name="agentx"></a> <h2>AgentX</h2>
<pre> To have the sub-agent communicate on a different socket, or with
different permissions, add these line to your snmpd.conf

	# socket path
	agentxsocket /tmp/agentx

	# perms socket directory userid groupid
	agentxperms 777 777 rstory rstory


and add this line to your subagent:

	netsnmp_ds_set_string(NETSNMP_DS_APPLICATION_ID, NETSNMP_DS_AGENT_X_SOCKET, "/tmp/agentx");

*before* you call init_agent().

 </pre>

<a name="install"></a><h2>install</h2>
<pre> INSTALL_PREFIX goes before everything.. so, with the defaults, just
setting INSTALL_PREFIX=/tmp would result in /tmp/usr/local.. 
so INSTALL_PREFIX=/tmp prefix=/usr exec_prefix=/usr would go into /tmp/usr
 </pre>

<a name="disable"></a><h2>disable</h2>
<pre> If you are using net-snmp Version >= 5.1, then the following configure
options may be useful to you:

  --disable-agent                 Do not build the agent (snmpd).
  --disable-applications          Do not build the apps (snmpget, ...).
  --disable-manuals               Do not install the manuals.
  --disable-scripts               Do not install the scripts (mib2c, ...).
  --disable-mibs                  Do not install the mib files.
  --disable-mib-loading            Do not include code that parses and
                                   manipulates the mib files.
 </pre>

<a name="errors"></a><h2>errors</h2>
<pre> from RFC 3416:

                   noError(0),
                   tooBig(1),
                   noSuchName(2),      -- for proxy compatibility
                   badValue(3),        -- for proxy compatibility
                   readOnly(4),        -- for proxy compatibility
                   genErr(5),
                   noAccess(6),
                   wrongType(7),
                   wrongLength(8),
                   wrongEncoding(9),
                   wrongValue(10),
                   noCreation(11),
                   inconsistentValue(12),
                   resourceUnavailable(13),
                   commitFailed(14),
                   undoFailed(15),
                   authorizationError(16),
                   notWritable(17),
                   inconsistentName(18)
 </pre>

<a name="bits"></a><h2>bits</h2>
<pre> SNMPv1 use BIT STRINGs (RFC 1212, 5.1.1):

          (3)  An object with BIT STRING syntax containing no more than
               32 bits becomes an INTEGER defined as a sum; otherwise if
               more than 32 bits are present, the object becomes an
               OCTET STRING, with the bits numbered from left-to-right,
               in which the least significant bits of the last octet may
               be "reserved for future use".

SNMPv2 and beyond uses BITS (RFC 3417, 8.1):

   (3)   When encoding an object whose syntax is described using the
         BITS construct, the value is encoded as an OCTET STRING, in
         which all the named bits in (the definition of) the bitstring,
         commencing with the first bit and proceeding to the last bit,
         are placed in bits 8 (high order bit) to 1 (low order bit) of
         the first octet, followed by bits 8 to 1 of each subsequent
         octet in turn, followed by as many bits as are needed of the
         final subsequent octet, commencing with bit 8.  Remaining bits,
         if any, of the final octet are set to zero on generation and
         ignored on receipt.
 </pre>

<a name="embedded"></a> <h2>embedded perl</h2>
<pre> Add the following line to snmpd.conf:
 
   perl do "/path/to/perl_module.pl"


To test:

1) Try staring up snmpd, like so: 'snmpd -Dperl'. Check your log files for:

  perl: initializing perl (/tmp/snmp_perl.pl)
  starting perl_module.pl
  perl_module.pl loaded ok
  registering at netSnmp.999

If you get:

  perl: initializing perl (/usr/local/share/snmp/snmp_perl.pl)
  Can't open perl script "/usr/local/share/snmp/snmp_perl.pl": No such file or directory
  embedded perl support failed to initalize

Then you need to locate snmp_perl.pl, and put it in the correct path, OR put
the path in your snmpd.conf:

	perlInitFile /tmp/snmp_perl.pl


2) Once it's loaded ok, try a walk:

	snmpwalk -v2c -c public localhost netSnmp.999

You should see something like this in your logs:

 refs: NetSNMP::agent::netsnmp_mib_handler, NetSNMP::agent::reginfo, NetSNMP::agent::netsnmp_agent_request_info, NetSNMP::agent::netsnmp_request_infoPtr
processing a request of type 161
   processing request of nsTransactionEntry.3
    .1.3.6.1.4.1.8072.999.1.2.1 -> hello world
   finished processing

3) If not, maybe check /path/to/perl_module.pl and make sure it is executable.

Hope that helps.

 </pre>

<a name="smux"></a> <h2>SMUX</h2>
<pre> To turn off SMUX when you don't have the options of recompiling from source
to disable SMUX support, you have to give it an invalid IP address to bind
to. This may be OS specific. On Linux, if I put this in my snmpd.conf:

	smuxsocket 1.0.0.0

I get an error at startup, and lsof or netstat show that snmpd is no longer
listenting on port 199. If you get and error message about the smuxsocket
token not being recongnized, then you're out of luck. You'll have to recompile
from source (or just use local firewall rules to block connections to port
199).
 </pre>

<a name="entid"></a> <h2>Enterprise OID</h2>
<pre> From: Dave Shield, RObert Story

Recent Versions (5.x)
---------------------
If you want to *just* change the sysObjectID numbering,
(and leave the notifications using the Net-SNMP enterprise OID)
then use  --with-enterprise-sysoid
Or you could just use the snmpd.conf directive 'sysobjectid'
to set this at run time.


If you want to *just* change enterprise-specific notification OID
(and leave the sysObjectID using the Net-SNMP values)
then use  --with-enterprise-notification-oid


If you want to change *both* of these,
then use --with-enterprise-oid

Older Versions (4.2.x)
----------------------
In older version, you have to manuall update the version_id in
agent/agent_trap.c:80

   oid version_id[]    = { EXTENSIBLEMIB, AGENTID, OSTYPE };

 </pre>

<a name="autodeps"></a> <h2>Automatic dependencies</h2>
<pre> For auto-dependencies, add the following to your Makefile:

#
# Build rules
#
%.d : %.c
	@echo "Generating makefile $@ ..."
	@set -e; $(CC) -M $(COPTS) $(CFLAGS) $(CPPFLAGS) $< \
	| sed 's/\($*\)\.o[ :]*/\1.o $@ : /g' > $@; \
	[ -s $@ ] || $(RM) $(RMFLAGS) $@

include $(SOURCES:.c=.d)

 </pre>

<a name="cross"></a> <h2>Cross compiling</h2>
<pre> From the net-snmp INSTALL file:

 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Specifying the System Type
==========================

   There may be some features `configure' can not figure out
automatically, but needs to determine by the type of host the package
will run on.  Usually `configure' can figure that out, but if it prints
a message saying it can not guess the host type, give it the
`--host=TYPE' option.  TYPE can either be a short name for the system
type, such as `sun4', or a canonical name with three fields:
     CPU-COMPANY-SYSTEM

See the file `config.sub' for the possible values of each field.  If
`config.sub' isn't included in this package, then this package doesn't
need to know the host type.

   If you are building compiler tools for cross-compiling, you can also
use the `--target=TYPE' option to select the type of system they will
produce code for and the `--build=TYPE' option to select the type of
system on which you are compiling the package.

 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

The most important configure options are:

	--with-cc=[cross-compiler]
	--with-ld=[cross-linker]
	--target=[target-environment]
	--with-endianness=[big|little]

Other potentially useful options:

	--with-cflags="..."
	--with-ldlags="..."
	--with-ar=/path/ar

	--enable-mini-agent
	--enable-shared="no"
	--without-pic

Two simple examples of cross-compiling:

./configure --target=ppc-linux --with-cc=ppc_405-gcc --with-endianness=big

./configure --target=powerpc-snmc-linux-gnu --build=i386-redhat-linux \
        --with-endianness=big

A more complex example involves setting environment variables for all
the flags for the tools needed for the cross compile:

   export TOOLPATH=/opt/hardhat/devkit/ppc/405
   export PATH=$TOOLPATH/bin:$PATH
   export CFLAGS=' -g -fPIC -msoft-float -D_SOFT_FLOAT -Dlinux -mcpu=403'
   export CPPFLAGS='-I$TOOLPATH/include -I$TOOLPATH/target/usr/include'
   export ASFLAGS='-g -gstabs'
   export LDFLAGS='-Wl,-soname,-Bdynamic -lc' 
   export LIB='ar rcu' 

   ./configure --build=i686-pc-linux-gnu  --host=powerpc \
           --target=powerpc-hardhat-linux-gnu --with-endianness=big


 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

The mibgroup section is the most OS specific part of the agent. It's likely
that you will have to remove some of them. You just need to figure out which
ones to remove. 

For example, agent/mibgroup/mibII/tcpTable.c is a common module that doesn't
work on new platforms. So if it isn't working, omit it during configure, like
so:

	./configure --with-out-mib-modules=mibII/tcpTable


Alternatively, you could work the other way. Start with a minimal
configuration:

	./configure --enable-mini-agent

and then start adding MIB modules one-by-one:

	./configure --enable-mini-agent
                    --with-mib-modules=mibII/system_mib,mibII/sysORTable


 </pre>

<a name="static"></a> <h2>Static linking</h2>
<pre> mXaureliu: I want to compile the 5.1 snmptrapd binary with statically linked libraries.. Can anyone help me with this? Is it just a simple configure switch
rstory: mXaureliu: you want static snmp libraries, or totally static (system libraries too)?
mXaureliu: totally static.. everything in one executable
mXaureliu: actually, how do i do both ways?
rstory: for snmp libs, try 'configure --enable-shared=no'.. that won't build the shared libraries
rstory: (though if you have previous versions of net-snmp libraries installed, the linker might pick those up and try and use them)
rstory: for totally static, you'll have to tweak the Makefile
rstory: add -Bstatic to LDFLAGS

[note: actually, for totally static, 'configure --with-ldflags=-Bstatic']
 </pre>

<a name="readfds"></a> <h2>readfds</h2>
<pre> > can you please tell me the meaning of the third argument. obviously the 
> first parameter to register_readfd is a file descriptor and second is the 
> callback function.

Correct.
The third parameter is arbitrary data that you can specify when you
register the file descriptor, and will then be passed to the callback
function when it's invoked.


So if you were listening on two separate sockets, for very similar
types of data, then you could use the same callback for both and
use this third parameter to distinguish between them:


	fd1 = open( "/proc/tweedledum" );
	fd2 = open( "/proc/tweedledee" );

	register_readfd( fd1, who_broke_the_rattle(), "tweedledee" );
	register_readfd( fd2, who_broke_the_rattle(), "tweedledum" );


void
who_broke_the_rattle( int fd, void *data )
{
    char *he_did = (char *)data;

    printf("%s broke the rattle!\n", he_did );
}

 </pre>

<a name="sharing"></a> <h2>sharing data</h2>
<pre> If two modules are compiled into the same agent/subagent, then just use a
normal C global var. No need to involve net-snmp in the process.

if they are different sub-agents, you are better off using tradition IPC
mechanisms. there is no net-snmp api for sharing data between subagents.

That said, *IF* you only need the data during processing of GET requests, or
when you aren't processing a request at all, you send a snmp request to the
master, which will query the other subagent. If you are processing a GET
request and are compiled into the master, you will have to delegate the
current request).

It's a little inefficient, compared to direct communication w/the other
subagent and it *will not* work during set processing.
 </pre>

<a name="tokens"></a> <h2>Debug Tokens</h2>
<pre> Some of the more common ones are:

   Agent: agent, agentx, dlmod, handler, helper, snmpd, trap, table
   MIBs: init_mib, mib_init, parse-file, parse-mibs
   Apps: read_config

Add them to your snmp.conf like so:

   # optionally turn on time stamps
   logTimestamp true
   doDebugging 1
   debugTokens agentx/config

If you put them in a different conf file, like snmpd.conf or myapp.conf,
prefix each with '[snmp]', like so:

   [snmp] doDebugging 1


This list was generated by running the following command in the main CVS branch:

find . -name \"*.c\" -print | xargs grep DEBUGMSGT | grep \" | cut -f 2 -d\" | sort -u

add
agent_handler
agent_registry
agent_set
agentx
agentx_build
agentx_build_varbind
agentx/config
agentx/config/retries
agentx/config/timeout
agentx/master
agentx/subagent
agentx/subgaent
asn_realloc
auto_nlist
build_oid_noalloc
build_oid_segment
callback
callback_clear
check_getnext_results
clear_nsap_list
compare:index
comparex
container
container_iterator
container_iterator:results
container:null:
container:null:find
container:null:find_next
container:null:for_each
container:null:free
container:null:get_null
container:null:get_null_factory
container:null:get_null_noalloc
container:null:insert
container:null:remove
container:null:size
container_registry
daemonize
deinit_usm_post_config
delayed_instance
dlmod
dump_etimelist
encode_keychange
example
example_data_set
example_notification
example_scalar_int
fixup_mib_directory
generate_Ku
generate_kul
get_mib_directory
handler:calling
handler:inject
handler::register
handler_registry
handler:returned
header_complex
header_complex_add_data
header_complex_dump
header_complex_extract_entry
header_complex_generate_oid
header_complex_generate_varoid
header_complex_parse_oid
header_complex_test
helper:baby_steps
helper:cache_handler
helper:debug
helper:instance
helper:mfd
helper:null
helper:read_only
helper:row_merge
helper:scalar
helper:scalar_group
helper:serialize
helper:stash_cache
helper:table
helper:watcher
helper:watcher:spinlock
helper:watcher:timestamp
host/hr_device
host/hr_disk
host/hr_filesys
host/hr_inst
host/hr_network
host/hr_partition
host/hr_print
host/hr_proc
host/hr_storage
host/hr_swinst
host/hr_swrun
host/hr_swrun::GetNextHR_SWRun
host/hr_system
hr_proc
initialize_table_ipCidrRouteTable
initialize_table_mteEventNotificationTable
initialize_table_mteEventTable
initialize_table_netSnmpHostsTable
initialize_table_nlmLogTable
initialize_table_nlmLogVariableTable
initialize_table_nsModuleTable
initialize_table_nsTransactionTable
init_mib
init_usm
injectHandler
kernel_sunos5
ksm
lcd_get_enginetime
lcd_get_enginetime_ex
lcd_set_enginetime
log_notification
md5
mfd
mibII/at
mibII/icmp
mibII/interfaces
mibII/ip
mibII/ipv6
mibII/mta_sendmail.c:mta_sendmail_parse_config
mibII/mta_sendmail.c:open_sendmailst
mibII/mta_sendmail.c:read_sendmailcf
mibII/snmp_mib
mibII/sysORTable
mibII/tcpScalar
mibII/tcpTable
mibII/udpScalar
mibII/udpTable
mibII/vacm_vars
mibII/var_route
mib_init
mte_disco
mteEventTable:send_events
mteObjectsTable
mteTriggerBooleanTable
mteTriggerDeltaTable
mteTriggerExistenceTable
mteTriggertable
mteTriggerTable
mteTriggerTest
mteTriggerTest:send_mte_trap
mteTriggerThresholdTable
netsnmp_aal5pvc
netsnmp_agent_check_packet
netsnmp_deregister_agent_nsap
netsnmp_ds_handle_config
netsnmp_ds_set_boolean
netsnmp_ds_set_int
netsnmp_ds_set_string
netsnmp_ds_set_void
netsnmp_ds_toggle_boolean
netsnmp_instance_counter32_handler
netsnmp_instance_int_handler
netsnmp_instance_long_handler
netsnmp_instance_ulong_handler
netsnmp_ipx
netsnmp_register_agent_nsap
netsnmp_register_mib_table_row
netsnmp_sockaddr_in
netsnmp_sockaddr_in6
netsnmp_sockaddr_ipx
netsnmp_table_data_set
netsnmp_tcp
netsnmp_tcp6
netsnmp_udp
netsnmp_udp6
netsnmp_udp6_getSecName
netsnmp_udp6_parse_security
netsnmp_udp_getSecName
netsnmp_udp_parse_security
netsnmp_unix
netsnmp_unix_getSecName
netsnmp_unix_parse_security
netsnmp_unix_transport
netstat:if
notification_log
nsCacheScalars
nsDebugScalars
object_monitor
old_api
output
override
parse-file
parse-mibs
parse_oid
parse_oid_indexes
perl
proc
proxy
proxy_args
proxy_config
proxy_init
read_config
read_config_copy_word
read_config_files
read_config:forward
read_config:initmib
read_config_read_data
read_config_read_memory
read_config_read_objid
read_config_read_octet_string
read_config_store_data_prefix
read_config:traphandle
register_exceptfd
register_index
register_mib
register_readfd
register_signal
register_writefd
report
results
scalar_int
scapi
scopedPDU_parse
send_notifications
sess_async_send
_sess_open
sess_process_packet
sess_read
sess_resend
sess_select
setting auth type: \
signal
smux
smux_conf
smux_init
smux/snmp_bgp
smux/snmp_ospf
smux/snmp_rip2
snmp_agent
snmp_alarm
snmp_api
snmp_build
snmp_clean_persistent
snmp_config
snmpd
snmpd/main
snmpd_ports
snmpd_register_app_config_handler
snmpd/select
snmpEngine
snmpNotifyFilterProfileTable
snmpNotifyFilterTable
snmpNotifyTable
snmp_parse
snmp_parse_args
snmp_parse_oid
snmp_pdu_realloc_rbuild
snmp_save_persistent
snmp_send
snmp_sess_add
snmp_sess_close
snmp_sess_open
snmpSetSerialNo
snmp_store
snmpTargetAddrEntry
snmpTargetParamsEntry
snmptrapd
snmpv3
snmpv3_parse
sprint_by_type
stash_cache
subtree
table_array
table_array:get
table_array:group
table_data_add_data
table_iterator
table_set_add_row
take_snapshot
target_counters
target_sessions
tdomain
testhandler
testhandler_table
transport_callback
trap
trapsess
tunnel
ucdDemoPublic
ucd-snmp/disk
ucd-snmp/disk:
ucd-snmp/memory
ucd-snmp/pass
ucd-snmp/pass_persist
ucd-snmp/proc
ucd-snmp/versioninfo
ucd-snmp/vmstat_aix4.c:update_stats
ucd-snmp/vmstat_dynix.c:update_stats
ucd-snmp/vmstat_hpux.c:update_stats
ucd-snmp/vmstat_solaris2.c:update_stats
unlink_tree
unload-mib
unregister_exceptfd
unregister_readfd
unregister_signal
unregister_writefd
usm
usmUser
util_funcs
vacm:checkSubtree
vacm:getView
versioninfo
vmstat
yyyinjectHandler
 </pre>

<a name="steps"></a> <h2>Baby Steps Flow</h2>
<pre>     /**
     * Baby Steps Flow diagram (rev 2003.09.29.1330)
     *
     * Legend: (test) [optional] &lt;required>
     *
     * OLD              NEW
     * ========  ============================================
     * +++           [pre_request]
     *                    |
     *               (row exists?) N ->(row_creation) N >-->+
     *                    |                   | Y           |
     *                    |&lt;------------------+             |
     *                   \|/                               \|/
     * RESERVE1  &lt;object_syntax_checks>                     |
     *                    |                                 | 
     *                  (err?)  Y >------------------------>+
     *                    |                                 |
     *                   \|/                               \|/
     * +++          (row existed?) N --->[row_creation]     |
     *                    |                   |             |
     *                    |&lt;--------------N (err?)          |
     *                    |                   | Y           |
     *                    |                   |             |
     *                    |       [row_creation_cleanup]--->+
     *                   \|/                                |
     * RESERVER2     [undo_setup]                           |
     *                    |                                 |
     *                  (err?)  Y --->-------->--------->+  |
     *                    |                              | \|/
     * ACTION        &lt;set_values>                        |  |
     *                    |                              |  |
     *                  (err?)  Y >---------+           \|/ |
     *                    |                 |            |  |
     * +++        [consistency_checks]      |            |  |
     *                    |                \|/           |  |
     * UNDO             (err?)  Y >-------[undo]-------->+  |
     *                    |                              |  |
     *            [reversible_commit]                    |  |
     * +++                |                              | \|/
     *                  (err?)  Y >--[reverse_commit]    |  |
     *                    |              |               |  |
     * COMMIT        &lt;final_commit>      |               |  |
     *                    |              |               |  |
     *                  (err?)  Y >--[log msg]           |  |
     *                    |              |               |  |
     *                    |             \|/             \|/ |
     *                    | &lt;-----------&lt;+---&lt;-----------+  |
     *                   \|/                                |
     * FREE          [undo_cleanup]                         |
     *                    |                                \|/
     *                    |&lt;--------------&lt;-----------------+
     *                   \|/
     *               [post_request]
     */
 </pre>

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