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PPP: set PPP_NUM_TIMEOUTS_PER_PCB value to computed number of simultaneous timers

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A deep analysis of simultaneously running timers showed we can use a
slightly smaller value for PPP_NUM_TIMEOUTS_PER_PCB, value which was
arbitrarily chosen to a safe value based on the number of enabled PPP
features. Add the boring and long analysis to the end of our internal
header file and use the result in ppp_opts.h.

Signed-off-by: Sylvain Rochet <gradator@gradator.net>
This commit is contained in:
Sylvain Rochet 2018-06-18 01:11:01 +02:00
parent 58b5a5fc5a
commit e4e0fc4193
2 changed files with 91 additions and 2 deletions
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88
src/include/netif/ppp/ppp_impl.h
View File

@ -621,6 +621,94 @@ void ppp_dump_packet(ppp_pcb *pcb, const char *tag, unsigned char *p, int len);
/* dump packet to debug log if interesting */
#endif /* PRINTPKT_SUPPORT */
/*
* Number of necessary timers analysis.
*
* PPP use at least one timer per each of its protocol, but not all protocols are
* active at the same time, thus the number of necessary timeouts is actually
* lower than enabled protocols. Here is the actual necessary timeouts based
* on code analysis.
*
* Note that many features analysed here are not working at all and are only
* there for a comprehensive analysis of necessary timers in order to prevent
* having to redo that each time we add a feature.
*
* Timer list
*
* | holdoff timeout
* | low level protocol timeout (PPPoE or PPPoL2P)
* | LCP delayed UP
* | LCP retransmit (FSM)
* | LCP Echo timer
* .| PAP or CHAP or EAP authentication
* . | ECP retransmit (FSM)
* . | CCP retransmit (FSM) when MPPE is enabled
* . | CCP retransmit (FSM) when MPPE is NOT enabled
* . | IPCP retransmit (FSM)
* . .| IP6CP retransmit (FSM)
* . . | Idle time limit
* . . | Max connect time
* . . | Max octets
* . . | CCP RACK timeout
* . . .
* PPP_PHASE_DEAD
* PPP_PHASE_HOLDOFF
* | . . .
* PPP_PHASE_INITIALIZE
* | . . .
* PPP_PHASE_ESTABLISH
* | . . .
* |. . .
* | . .
* PPP_PHASE_AUTHENTICATE
* | . .
* || . .
* PPP_PHASE_NETWORK
* | || . .
* | ||| .
* PPP_PHASE_RUNNING
* | .|||||
* | . ||||
* PPP_PHASE_TERMINATE
* | . ||||
* PPP_PHASE_NETWORK
* |. .
* PPP_PHASE_ESTABLISH
* PPP_PHASE_DISCONNECT
* PPP_PHASE_DEAD
*
* Alright, PPP basic retransmission and LCP Echo consume one timer.
* 1
*
* If authentication is enabled one timer is necessary during authentication.
* 1 + PPP_AUTH_SUPPORT
*
* If ECP is enabled one timer is necessary before IPCP and/or IP6CP, one more
* is necessary if CCP is enabled (only with MPPE support but we don't care much
* up to this detail level).
* 1 + ECP_SUPPORT + CCP_SUPPORT
*
* If CCP is enabled it might consume a timer during IPCP or IP6CP, thus
* we might use IPCP, IP6CP and CCP timers simultaneously.
* 1 + PPP_IPV4_SUPPORT + PPP_IPV6_SUPPORT + CCP_SUPPORT
*
* When entering running phase, IPCP or IP6CP is still running. If idle time limit
* is enabled one more timer is necessary. Same for max connect time and max
* octets features. Furthermore CCP RACK might be used past this point.
* 1 + PPP_IPV4_SUPPORT + PPP_IPV6_SUPPORT -1 + PPP_IDLETIMELIMIT + PPP_MAXCONNECT + MAXOCTETS + CCP_SUPPORT
*
* IPv4 or IPv6 must be enabled, therefore we don't need to take care the authentication
* and the CCP + ECP case, thus reducing overall complexity.
* 1 + LWIP_MAX(PPP_IPV4_SUPPORT + PPP_IPV6_SUPPORT + CCP_SUPPORT, PPP_IPV4_SUPPORT + PPP_IPV6_SUPPORT -1 + PPP_IDLETIMELIMIT + PPP_MAXCONNECT + MAXOCTETS + CCP_SUPPORT)
*
* We don't support PPP_IDLETIMELIMIT + PPP_MAXCONNECT + MAXOCTETS features
* and adding those defines to ppp_opts.h just for having the value always
* defined to 0 isn't worth it.
* 1 + LWIP_MAX(PPP_IPV4_SUPPORT + PPP_IPV6_SUPPORT + CCP_SUPPORT, PPP_IPV4_SUPPORT + PPP_IPV6_SUPPORT -1 + CCP_SUPPORT)
*
* Thus, the following is enough for now.
* 1 + PPP_IPV4_SUPPORT + PPP_IPV6_SUPPORT + CCP_SUPPORT
*/
#endif /* PPP_SUPPORT */
#endif /* LWIP_HDR_PPP_IMPL_H */

5
src/include/netif/ppp/ppp_opts.h
View File

@ -82,10 +82,11 @@
/**
* PPP_NUM_TIMEOUTS_PER_PCB: the number of sys_timeouts running in parallel per
* ppp_pcb. This is a conservative default which needs to be checked...
* ppp_pcb. See the detailed explanation at the end of ppp_impl.h about simultaneous
* timers analysis.
*/
#ifndef PPP_NUM_TIMEOUTS_PER_PCB
#define PPP_NUM_TIMEOUTS_PER_PCB 6
#define PPP_NUM_TIMEOUTS_PER_PCB (1 + PPP_IPV4_SUPPORT + PPP_IPV6_SUPPORT + CCP_SUPPORT)
#endif
/* The number of sys_timeouts required for the PPP module */