VyOS 1.2.3 IPSec logging

I think you need

set system syslog global facility daemon level notice
set system syslog global facility protocols level all

You also can set log-modes fro ipsec

vyos@R1# set vpn ipsec logging log-modes 
Possible completions:
   dmn          Debug log option for strongSwan
   mgr          Debug log option for strongSwan
   ike          Debug log option for strongSwan
   chd          Debug log option for strongSwan
   job          Debug log option for strongSwan
   cfg          Debug log option for strongSwan
   knl          Debug log option for strongSwan
   net          Debug log option for strongSwan
   asn          Debug log option for strongSwan
   enc          Debug log option for strongSwan
   lib          Debug log option for strongSwan
   esp          Debug log option for strongSwan
   tls          Debug log option for strongSwan
   tnc          Debug log option for strongSwan
   imc          Debug log option for strongSwan
   imv          Debug log option for strongSwan
   pts          Debug log option for strongSwan
   any          Debug log option for strongSwan

Each logging message also has a source from which subsystem in the daemon the log came from:

  • app: applications other than daemons
  • asn: Low-level encoding/decoding (ASN.1, X.509 etc.)
  • cfg: Configuration management and plugins
  • chd: CHILD_SA/IPsec SA
  • dmn: Main daemon setup/cleanup/signal handling
  • enc: Packet encoding/decoding encryption/decryption operations
  • esp: libipsec library messages
  • ike: IKE_SA/ISAKMP SA
  • imc: Integrity Measurement Collector
  • imv: Integrity Measurement Verifier
  • job: Jobs queuing/processing and thread pool management
  • knl: IPsec/Networking kernel interface
  • lib: libstrongwan library messages
  • mgr: IKE_SA manager, handling synchronization for IKE_SA access
  • net: IKE network communication
  • pts: Platform Trust Service
  • tls: libtls library messages
  • tnc: Trusted Network Connect