.SH LOGGER CONFIGURATION Options in .BR strongswan.conf (5) provide a much more flexible way to configure loggers for the IKE daemon charon than using the .B charondebug option in .BR ipsec.conf (5). .PP .BR Note : If any loggers are specified in strongswan.conf, .B charondebug does not have any effect. .PP There are currently two types of loggers: .TP .B File loggers Log directly to a file and are defined by specifying the full path to the file as subsection in the .B charon.filelog section. To log to the console the two special filenames .BR stdout " and " stderr can be used. .TP .B Syslog loggers Log into a syslog facility and are defined by specifying the facility to log to as the name of a subsection in the .B charon.syslog section. The following facilities are currently supported: .BR daemon " and " auth . .PP Multiple loggers can be defined for each type with different log verbosity for the different subsystems of the daemon. .SS Subsystems .TP .B dmn Main daemon setup/cleanup/signal handling .TP .B mgr IKE_SA manager, handling synchronization for IKE_SA access .TP .B ike IKE_SA .TP .B chd CHILD_SA .TP .B job Jobs queueing/processing and thread pool management .TP .B cfg Configuration management and plugins .TP .B knl IPsec/Networking kernel interface .TP .B net IKE network communication .TP .B asn Low-level encoding/decoding (ASN.1, X.509 etc.) .TP .B enc Packet encoding/decoding encryption/decryption operations .TP .B tls libtls library messages .TP .B esp libipsec library messages .TP .B lib libstrongwan library messages .TP .B tnc Trusted Network Connect .TP .B imc Integrity Measurement Collector .TP .B imv Integrity Measurement Verifier .TP .B pts Platform Trust Service .SS Loglevels .TP .B -1 Absolutely silent .TP .B 0 Very basic auditing logs, (e.g. SA up/SA down) .TP .B 1 Generic control flow with errors, a good default to see whats going on .TP .B 2 More detailed debugging control flow .TP .B 3 Including RAW data dumps in Hex .TP .B 4 Also include sensitive material in dumps, e.g. keys .SS Example .PP .EX charon { filelog { /var/log/charon.log { time_format = %b %e %T append = no default = 1 } stderr { ike = 2 knl = 3 ike_name = yes } } syslog { # enable logging to LOG_DAEMON, use defaults daemon { } # minimalistic IKE auditing logging to LOG_AUTHPRIV auth { default = -1 ike = 0 } } } .EE .SH JOB PRIORITY MANAGEMENT Some operations in the IKEv2 daemon charon are currently implemented synchronously and blocking. Two examples for such operations are communication with a RADIUS server via EAP-RADIUS, or fetching CRL/OCSP information during certificate chain verification. Under high load conditions, the thread pool may run out of available threads, and some more important jobs, such as liveness checking, may not get executed in time. .PP To prevent thread starvation in such situations job priorities were introduced. The job processor will reserve some threads for higher priority jobs, these threads are not available for lower priority, locking jobs. .SS Implementation Currently 4 priorities have been defined, and they are used in charon as follows: .TP .B CRITICAL Priority for long-running dispatcher jobs. .TP .B HIGH INFORMATIONAL exchanges, as used by liveness checking (DPD). .TP .B MEDIUM Everything not HIGH/LOW, including IKE_SA_INIT processing. .TP .B LOW IKE_AUTH message processing. RADIUS and CRL fetching block here .PP Although IKE_SA_INIT processing is computationally expensive, it is explicitly assigned to the MEDIUM class. This allows charon to do the DH exchange while other threads are blocked in IKE_AUTH. To prevent the daemon from accepting more IKE_SA_INIT requests than it can handle, use IKE_SA_INIT DROPPING. .PP The thread pool processes jobs strictly by priority, meaning it will consume all higher priority jobs before looking for ones with lower priority. Further, it reserves threads for certain priorities. A priority class having reserved .I n threads will always have .I n threads available for this class (either currently processing a job, or waiting for one). .SS Configuration To ensure that there are always enough threads available for higher priority tasks, threads must be reserved for each priority class. .TP .BR charon.processor.priority_threads.critical " [0]" Threads reserved for CRITICAL priority class jobs .TP .BR charon.processor.priority_threads.high " [0]" Threads reserved for HIGH priority class jobs .TP .BR charon.processor.priority_threads.medium " [0]" Threads reserved for MEDIUM priority class jobs .TP .BR charon.processor.priority_threads.low " [0]" Threads reserved for LOW priority class jobs .PP Let's consider the following configuration: .PP .EX charon { processor { priority_threads { high = 1 medium = 4 } } } .EE .PP With this configuration, one thread is reserved for HIGH priority tasks. As currently only liveness checking and stroke message processing is done with high priority, one or two threads should be sufficient. .PP The MEDIUM class mostly processes non-blocking jobs. Unless your setup is experiencing many blocks in locks while accessing shared resources, threads for one or two times the number of CPU cores is fine. .PP It is usually not required to reserve threads for CRITICAL jobs. Jobs in this class rarely return and do not release their thread to the pool. .PP The remaining threads are available for LOW priority jobs. Reserving threads does not make sense (until we have an even lower priority). .SS Monitoring To see what the threads are actually doing, invoke .IR "ipsec statusall" . Under high load, something like this will show up: .PP .EX worker threads: 2 or 32 idle, 5/1/2/22 working, job queue: 0/0/1/149, scheduled: 198 .EE .PP From 32 worker threads, .IP 2 are currently idle. .IP 5 are running CRITICAL priority jobs (dispatching from sockets, etc.). .IP 1 is currently handling a HIGH priority job. This is actually the thread currently providing this information via stroke. .IP 2 are handling MEDIUM priority jobs, likely IKE_SA_INIT or CREATE_CHILD_SA messages. .IP 22 are handling LOW priority jobs, probably waiting for an EAP-RADIUS response while processing IKE_AUTH messages. .PP The job queue load shows how many jobs are queued for each priority, ready for execution. The single MEDIUM priority job will get executed immediately, as we have two spare threads reserved for MEDIUM class jobs. .SH IKE_SA_INIT DROPPING If a responder receives more connection requests per seconds than it can handle, it does not make sense to accept more IKE_SA_INIT messages. And if they are queued but can't get processed in time, an answer might be sent after the client has already given up and restarted its connection setup. This additionally increases the load on the responder. .PP To limit the responder load resulting from new connection attempts, the daemon can drop IKE_SA_INIT messages just after reception. There are two mechanisms to decide if this should happen, configured with the following options: .TP .BR charon.init_limit_half_open " [0]" Limit based on the number of half open IKE_SAs. Half open IKE_SAs are SAs in connecting state, but not yet established. .TP .BR charon.init_limit_job_load " [0]" Limit based on the number of jobs currently queued for processing (sum over all job priorities). .PP The second limit includes load from other jobs, such as rekeying. Choosing a good value is difficult and depends on the hardware and expected load. .PP The first limit is simpler to calculate, but includes the load from new connections only. If your responder is capable of negotiating 100 tunnels/s, you might set this limit to 1000. The daemon will then drop new connection attempts if generating a response would require more than 10 seconds. If you are allowing for a maximum response time of more than 30 seconds, consider adjusting the timeout for connecting IKE_SAs .RB ( charon.half_open_timeout ). A responder, by default, deletes an IKE_SA if the initiator does not establish it within 30 seconds. Under high load, a higher value might be required. .SH LOAD TESTS To do stability testing and performance optimizations, the IKE daemon charon provides the \fIload-tester\fR plugin. This plugin allows one to setup thousands of tunnels concurrently against the daemon itself or a remote host. .PP .B WARNING: Never enable the load-testing plugin on productive systems. It provides preconfigured credentials and allows an attacker to authenticate as any user. .PP .SS Configuration details For public key authentication, the responder uses the .B \(dqCN=srv, OU=load-test, O=strongSwan\(dq identity. For the initiator, each connection attempt uses a different identity in the form .BR "\(dqCN=c1-r1, OU=load-test, O=strongSwan\(dq" , where the first number inidicates the client number, the second the authentication round (if multiple authentication rounds are used). .PP For PSK authentication, FQDN identities are used. The server uses .BR srv.strongswan.org , the client uses an identity in the form .BR c1-r1.strongswan.org . .PP For EAP authentication, the client uses a NAI in the form .BR 100000000010001@strongswan.org . .PP To configure multiple authentication rounds, concatenate multiple methods using, e.g. .EX initiator_auth = pubkey|psk|eap-md5|eap-aka .EE .PP The responder uses a hardcoded certificate based on a 1024-bit RSA key. This certificate additionally serves as CA certificate. A peer uses the same private key, but generates client certificates on demand signed by the CA certificate. Install the Responder/CA certificate on the remote host to authenticate all clients. .PP To speed up testing, the load tester plugin implements a special Diffie-Hellman implementation called \fImodpnull\fR. By setting .EX proposal = aes128-sha1-modpnull .EE this wicked fast DH implementation is used. It does not provide any security at all, but allows one to run tests without DH calculation overhead. .SS Examples .PP In the simplest case, the daemon initiates IKE_SAs against itself using the loopback interface. This will actually establish double the number of IKE_SAs, as the daemon is initiator and responder for each IKE_SA at the same time. Installation of IPsec SAs would fail, as each SA gets installed twice. To simulate the correct behavior, a fake kernel interface can be enabled which does not install the IPsec SAs at the kernel level. .PP A simple loopback configuration might look like this: .PP .EX charon { # create new IKE_SAs for each CHILD_SA to simulate # different clients reuse_ikesa = no # turn off denial of service protection dos_protection = no plugins { load-tester { # enable the plugin enable = yes # use 4 threads to initiate connections # simultaneously initiators = 4 # each thread initiates 1000 connections iterations = 1000 # delay each initiation in each thread by 20ms delay = 20 # enable the fake kernel interface to # avoid SA conflicts fake_kernel = yes } } } .EE .PP This will initiate 4000 IKE_SAs within 20 seconds. You may increase the delay value if your box can not handle that much load, or decrease it to put more load on it. If the daemon starts retransmitting messages your box probably can not handle all connection attempts. .PP The plugin also allows one to test against a remote host. This might help to test against a real world configuration. A connection setup to do stress testing of a gateway might look like this: .PP .EX charon { reuse_ikesa = no threads = 32 plugins { load-tester { enable = yes # 10000 connections, ten in parallel initiators = 10 iterations = 1000 # use a delay of 100ms, overall time is: # iterations * delay = 100s delay = 100 # address of the gateway remote = # IKE-proposal to use proposal = aes128-sha1-modp1024 # use faster PSK authentication instead # of 1024bit RSA initiator_auth = psk responder_auth = psk # request a virtual IP using configuration # payloads request_virtual_ip = yes # enable CHILD_SA every 60s child_rekey = 60 } } } .EE .SH IKEv2 RETRANSMISSION Retransmission timeouts in the IKEv2 daemon charon can be configured globally using the three keys listed below: .PP .RS .nf .BR charon.retransmit_base " [1.8]" .BR charon.retransmit_timeout " [4.0]" .BR charon.retransmit_tries " [5]" .fi .RE .PP The following algorithm is used to calculate the timeout: .PP .EX relative timeout = retransmit_timeout * retransmit_base ^ (n-1) .EE .PP Where .I n is the current retransmission count. .PP Using the default values, packets are retransmitted in: .TS l r r --- lB r r. Retransmission Relative Timeout Absolute Timeout 1 4s 4s 2 7s 11s 3 13s 24s 4 23s 47s 5 42s 89s giving up 76s 165s .TE . .SH VARIABLES . The variables used above are configured as follows: .nf .na ${piddir} @piddir@ ${prefix} @prefix@ ${random_device} @random_device@ ${urandom_device} @urandom_device@ .ad .fi . .SH FILES . .nf .na /etc/strongswan.conf configuration file /etc/strongswan.d/ directory containing included config snippets /etc/strongswan.d/charon/ plugin specific config snippets .ad .fi . .SH SEE ALSO \fBipsec.conf\fR(5), \fBipsec.secrets\fR(5), \fBipsec\fR(8), \fBcharon-cmd\fR(8) .SH HISTORY Written for the .UR http://www.strongswan.org strongSwan project .UE by Tobias Brunner, Andreas Steffen and Martin Willi.