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http://bugs.exim.org/show_bug.cgi?id=579 Summary: smtp_reserve_hosts are not really guaranteed smtp_accept_reserve connections Product: Exim Version: 4.67 Platform: Other OS/Version: Linux Status: NEW Severity: bug Priority: medium Component: Mail Receipt AssignedTo: [EMAIL PROTECTED] ReportedBy: [EMAIL PROTECTED] CC: [email protected] The specification for smtp_accept_reserve states that "When smtp_accept_max is set greater than zero, this option specifies a number of SMTP connections that are reserved for connections from the hosts that are specified in smtp_reserve_hosts. [...] It is a guarantee that this group of hosts can always get at least smtp_accept_reserve connections." However, this is a weak guarantee, because only smtp_accept_max and smtp_accept_max_per_host (and some others) are checked in the main daemon loop, and in particular before incrementing smtp_accept_count, but smtp_accept_reserve (and smtp_load_reserve) is not checked until after forking and looking up the name of the connecting host (because the DNS lookup takes time). During this time, other connections can arrive, until smtp_accept_max is reached. The only solution I could think of so fare involves limiting smtp_reserve_hosts to a simple list of IP addresses/nets (which should normally be adequate to its purpose), so that matching the remote address can be done quickly enough. If no good enough solution exists, the specification should be clarified. As a workaround one can increase smtp_accept_max and smtp_accept_reserve until the probability that there will be smtp_accept_reserve simultaneous non-smtp_reserve_hosts connections waiting to be dropped is sufficiently small. -- Configure bugmail: http://bugs.exim.org/userprefs.cgi?tab=email -- ## List details at http://lists.exim.org/mailman/listinfo/exim-dev Exim details at http://www.exim.org/ ##
