Team A
[ZBX-16123] Self-written sender in bash - Header length Created: 2019 May 13 Updated: 2024 Apr 10 Resolved: 2019 May 14 |
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| Status: | Closed |
| Project: | ZABBIX BUGS AND ISSUES |
| Component/s: | Server (S) |
| Affects Version/s: | 4.0.7 |
| Fix Version/s: | None |
| Type: | Documentation task | Priority: | Minor |
| Reporter: | Dominique | Assignee: | Vladislavs Sokurenko |
| Resolution: | Fixed | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Environment: |
CentOS Linux release 7.4.1708 (Core) |
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| Team: | Team A |
| Sprint: | Sprint 52 (May 2019) |
| Description |
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We're using self-written senders on some dedicated systems. As described in 4 Header we used the example with bash. Sending is done by nc (netcat). example.sh DATA='{ "request":"sender data", "data":[ { "host":"host1", "key":"test.item[1]", "value":"0"}] }' printf -v LENGTH '%016x' "${#DATA}" PACK="" for i in {14..0..-2}; do PACK="$PACK\\x${LENGTH:$i:2}"; done printf "ZBXD\1$PACK%s" $DATA | \ nc -v -s 127.0.0.1 127.0.0.1 10051 Executing the code:
# ./example.sh
Ncat: Version 6.40 ( http://nmap.org/ncat )
Ncat: Connected to 127.0.0.1:10051.
Ncat: 218 bytes sent, 0 bytes received in 0.01 seconds.
Zabbix server log says: zabbix_server.log Message from 127.0.0.1 is longer than expected 109 bytes. Message ignored. For some reason the header length is calculated wrong in my example.sh. Executing the script without nc prints this:
ZBXDm{ZBXDm"request":"senderZBXDmdata",ZBXDm"data":[ZBXDm{ZBXDm"host":"host1",ZBXDm"key":"test.item[1]",ZBXDm"value":"0"}]ZBXDm}
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| Comments |
| Comment by Vladislavs Sokurenko [ 2019 May 13 ] |
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Please try this: DATA='{ "request":"sender data", "data":[ { "host":"host1", "key":"test.item[1]", "value":"0"}] }' printf -v LENGTH '%016x' "${#DATA}" PACK="" for i in {14..0..-2}; do PACK="$PACK\\x${LENGTH:$i:2}"; done printf "ZBXD\1$PACK%s" "$DATA" |
| Comment by Glebs Ivanovskis [ 2019 May 13 ] |
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Nice job, vso! Double quoting $DATA should solve the issue. Check out scripts attached to ZBXNEXT-3764, no one seems to complain about them. |
| Comment by Vladislavs Sokurenko [ 2019 May 14 ] |
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Updated following pages: |
| Comment by Dominique [ 2019 May 14 ] |
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Thanks, it's working with the double quotes! However, on some of our systems with a different bash version we still have issues: error
line 79: LENGTH: {14..0..-2}: syntax error: operand expected (error token is "{14..0..-2}")
bash version GNU bash, version 3.2.25(1)-release (i686-redhat-linux-gnu) |
| Comment by Vladislavs Sokurenko [ 2019 May 14 ] |
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Yes cyclone, scripts in ZBXNEXT-3764 look very interesting I will keep those in my mind ! Documentation has been updated to include quoting. |
| Comment by Vladislavs Sokurenko [ 2019 May 14 ] |
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This should do the trick Birchler DATA='{ "request":"sender data", "data":[ { "host":"host1", "key":"test.item[1]", "value":"0"}] }' printf -v LENGTH '%016x' "${#DATA}" PACK="" for (( i=14; i>=0; i-=2 )); do PACK="$PACK\\x${LENGTH:$i:2}"; done printf "ZBXD\1$PACK%s" "$DATA" |
| Comment by Dominique [ 2019 May 14 ] |
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Great, it works! Thank you for your support. |
| Comment by Vladislavs Sokurenko [ 2019 May 14 ] |
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Can you please confirm that edited script works for you ? |
| Comment by Dominique [ 2019 May 14 ] |
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Yes, it works for me, thank you vso. |
| Comment by Glebs Ivanovskis [ 2019 May 14 ] |
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{START..END..INCREMENT} syntax requires Bash v4.0+ according to this source. |