Suricata

I also got this on a pcap (but cant share the pcap itself/partly due to size too)

[23018] 17/6/2019 -- 02:17:17 - (util-checksum.c:89) <Info> (ChecksumAutoModeCheck) -- No packets with invalid checksum, assuming checksum offloading is NOT used                     
[23024] 17/6/2019 -- 02:33:17 - (snmp.rs:154) <Info> (<rust>) -- parse_snmp_v2 failed: Err(Error(Code([4, 7, 112, 1.. Tag)))                                                                                                                                                          
[23022] 17/6/2019 -- 02:33:18 - (snmp.rs:154) <Info> (<rust>) -- parse_snmp_v2 failed: Err(Error(Code([4...8, 5, 6, 1, 43, 5, 0], Tag)))                                                                                                                                                                  
[23025] 17/6/2019 -- 02:33:18 - (snmp.rs:154) <Info> (<rust>) -- parse_snmp_v2 failed: Err(Error(Code([4, 5, 99, 105, 115, 99, 111, ...], Tag)))                                                                                                                                                                   
[23020] 17/6/2019 -- 02:33:18 - (snmp.rs:154) <Info> (<rust>) -- parse_snmp_v2 failed: Err(Error(Code([4, 6, 48, 51, 57, 50, 97,...0], Tag)))
[23024] 17/6/2019 -- 02:33:19 - (snmp.rs:154) <Info> (<rust>) -- parse_snmp_v2 failed: Err(Error(Code([,,,,, 161)

Using

/opt/suricatagit/bin/suricata --build-info
This is Suricata version 5.0.0-dev (rev b5f3e0320)
Features: PCAP_SET_BUFF AF_PACKET HAVE_PACKET_FANOUT LIBCAP_NG LIBNET1.1 HAVE_HTP_URI_NORMALIZE_HOOK PCRE_JIT HAVE_NSS HAVE_LUA HAVE_LUAJIT HAVE_LIBJANSSON PROFILING TLS MAGIC RUST 
SIMD support: SSE_4_2 SSE_4_1 SSE_3 
Atomic intrisics: 1 2 4 8 16 byte(s)
64-bits, Little-endian architecture
GCC version 7.4.0, C version 199901
compiled with _FORTIFY_SOURCE=2
L1 cache line size (CLS)=64
thread local storage method: __thread
compiled with LibHTP v0.5.30, linked against LibHTP v0.5.30

Suricata Configuration:
  AF_PACKET support:                       yes
  eBPF support:                            no
  XDP support:                             no
  PF_RING support:                         no
  NFQueue support:                         no
  NFLOG support:                           no
  IPFW support:                            no
  Netmap support:                          no 
  DAG enabled:                             no
  Napatech enabled:                        no
  WinDivert enabled:                       no

  Unix socket enabled:                     yes
  Detection enabled:                       yes

  Libmagic support:                        yes
  libnss support:                          yes
  libnspr support:                         yes
  libjansson support:                      yes
  liblzma support:                         no
  hiredis support:                         no
  hiredis async with libevent:             no
  Prelude support:                         no
  PCRE jit:                                yes
  LUA support:                             yes, through luajit
  libluajit:                               yes
  libgeoip:                                yes
  Non-bundled htp:                         no
  Old barnyard2 support:                   no
  Hyperscan support:                       yes
  Libnet support:                          yes
  liblz4 support:                          yes

  Rust support:                            yes
  Rust strict mode:                        no
  Rust debug mode:                         no
  Rust compiler:                           rustc 1.32.0
  Rust cargo:                              cargo 1.32.0

  Python support:                          yes
  Python path:                             /usr/bin/python3
  Python version:                          Python 3.6.7
  Python distutils                         yes
  Python yaml                              yes
  Install suricatactl:                     yes
  Install suricatasc:                      yes
  Install suricata-update:                 not bundled

  Profiling enabled:                       yes
  Profiling locks enabled:                 no

Development settings:
  Coccinelle / spatch:                     yes
  Unit tests enabled:                      no
  Debug output enabled:                    no
  Debug validation enabled:                no

Generic build parameters:
  Installation prefix:                     /opt/suricatagit
  Configuration directory:                 /opt/suricatagit/etc/suricata/
  Log directory:                           /opt/suricatagit/var/log/suricata/

  --prefix                                 /opt/suricatagit
  --sysconfdir                             /opt/suricatagit/etc
  --localstatedir                          /opt/suricatagit/var
  --datarootdir                            /opt/suricatagit/share

  Host:                                    x86_64-pc-linux-gnu
  Compiler:                                gcc (exec name) / gcc (real)
  GCC Protect enabled:                     no
  GCC march native enabled:                yes
  GCC Profile enabled:                     no
  Position Independent Executable enabled: no
  CFLAGS                                   -g -O2 -march=native -I${srcdir}/../rust/gen/c-headers
  PCAP_CFLAGS                               -I/usr/include
  SECCFLAGS                                

This one is hard to guess :/ The provided test pcap did not result in any error/warning here.

My current supposition is that there is a mismatch, and that different SNMP versions are seen in the same UDP connection. That is what the standard requests, and the current parser is a bit (over)strict with that (it checks that SNMP requests/answers are all using the same version).

I propose several changes:
- reduce verbosity (it should be Debug. and there is an additional good reason because it contains the SNMP community string)
- change restriction on version: change the parse to correctly parse any version, and maybe just add an event if versions mismatch

I think it would be good to set events. If you can set the version mismatch separately from other issues that might be in play then we can see which ones trigger in the real world traffic.

What is the status of this ticket?