X-Git-Url: https://git.exim.org/users/jgh/exim.git/blobdiff_plain/dc7b3d368017727e9438fc7463b0841df1e4aa41..fc362fc531e0ffc898c784e09f097327f5814289:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 411eb988e..d4ebf464d 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -1985,10 +1985,9 @@ Two different types of DNS record for handling IPv6 addresses have been defined. AAAA records (analogous to A records for IPv4) are in use, and are currently seen as the mainstream. Another record type called A6 was proposed as better than AAAA because it had more flexibility. However, it was felt to be -over-complex, and its status was reduced to &"experimental"&. It is not known -if anyone is actually using A6 records. Exim has support for A6 records, but -this is included only if you set &`SUPPORT_A6=YES`& in &_Local/Makefile_&. The -support has not been tested for some time. +over-complex, and its status was reduced to &"experimental"&. Exim used to +have a compile option for including A6 record support but this has now been +withdrawn. @@ -6879,19 +6878,11 @@ is used on its own as the result. If the lookup does not succeed, the &`fail`& keyword causes a &'forced expansion failure'& &-- see section &<>& for an explanation of what this means. -The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, TLSA and TXT, -and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also -configured). If no type is given, TXT is assumed. When the type is PTR, -the data can be an IP address, written as normal; inversion and the addition of -&%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example: -.code -${lookup dnsdb{ptr=192.168.4.5}{$value}fail} -.endd -If the data for a PTR record is not a syntactically valid IP address, it is not -altered and nothing is added. +The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA +and TXT, and, when Exim is compiled with IPv6 support, AAAA. +If no type is given, TXT is assumed. -For any record type, if multiple records are found (or, for A6 lookups, if a -single record leads to multiple addresses), the data is returned as a +For any record type, if multiple records are found, the data is returned as a concatenation, with newline as the default separator. The order, of course, depends on the DNS resolver. You can specify a different separator character between multiple records by putting a right angle-bracket followed immediately @@ -6901,21 +6892,33 @@ ${lookup dnsdb{>: a=host1.example}} .endd It is permitted to specify a space as the separator character. Further white space is ignored. +For lookup types that return multiple fields per record, +an alternate field separator can be specified using a comma after the main +separator character, followed immediately by the field separator. + +.cindex "PTR record" "in &(dnsdb)& lookup" +When the type is PTR, +the data can be an IP address, written as normal; inversion and the addition of +&%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example: +.code +${lookup dnsdb{ptr=192.168.4.5}{$value}fail} +.endd +If the data for a PTR record is not a syntactically valid IP address, it is not +altered and nothing is added. .cindex "MX record" "in &(dnsdb)& lookup" .cindex "SRV record" "in &(dnsdb)& lookup" For an MX lookup, both the preference value and the host name are returned for each record, separated by a space. For an SRV lookup, the priority, weight, port, and host name are returned for each record, separated by spaces. -An alternate field separator can be specified using a comma after the main -separator character, followed immediately by the field separator. +The field separator can be modified as above. .cindex "TXT record" "in &(dnsdb)& lookup" .cindex "SPF record" "in &(dnsdb)& lookup" For TXT records with multiple items of data, only the first item is returned, -unless a separator for them is specified using a comma after the separator -character followed immediately by the TXT record item separator. To concatenate -items without a separator, use a semicolon instead. For SPF records the +unless a field separator is specified. +To concatenate items without a separator, use a semicolon instead. +For SPF records the default behaviour is to concatenate multiple items without using a separator. .code ${lookup dnsdb{>\n,: txt=a.b.example}} @@ -6925,6 +6928,15 @@ ${lookup dnsdb{spf=example.org}} It is permitted to specify a space as the separator character. Further white space is ignored. +.cindex "SOA record" "in &(dnsdb)& lookup" +For an SOA lookup, while no result is obtained the lookup is redone with +successively more leading components dropped from the given domain. +Only the primary-nameserver field is returned unless a field separator is +specified. +.code +${lookup dnsdb{>:,; soa=a.b.example.com}} +.endd + .section "Dnsdb lookup modifiers" "SECTdnsdb_mod" .cindex "dnsdb modifiers" .cindex "modifiers" "dnsdb" @@ -6964,6 +6976,17 @@ The default is &"never"&. See also the &$lookup_dnssec_authenticated$& variable. +.cindex timeout "dns lookup" +.cindex "DNS" timeout +Timeout for the dnsdb lookup can be controlled by a retrans modifier. +The form is &"retrans_VAL"& where VAL is an Exim time specification +(eg &"5s"&). +The default value is set by the main configuration option &%dns_retrans%&. + +Retries for the dnsdb lookup can be controlled by a retry modifier. +The form if &"retry_VAL"& where VAL is an integer. +The default count is set by the main configuration option &%dns_retry%&. + .section "Pseudo dnsdb record types" "SECID66" .cindex "MX record" "in &(dnsdb)& lookup" @@ -7013,7 +7036,7 @@ The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit authorization required but absent, or &"?"& for unknown. .cindex "A+" "in &(dnsdb)& lookup" -The pseudo-type A+ performs an A6 lookup (if configured) followed by an AAAA +The pseudo-type A+ performs an AAAA and then an A lookup. All results are returned; defer processing (see below) is handled separately for each lookup. Example: .code @@ -8942,7 +8965,7 @@ The field selectors marked as "RFC4514" above output a Distinguished Name string which is not quite parseable by Exim as a comma-separated tagged list -(the exceptions being elements containin commas). +(the exceptions being elements containing commas). RDN elements of a single type may be selected by a modifier of the type label; if so the expansion result is a list (newline-separated by default). @@ -9713,8 +9736,9 @@ the regular expression from string expansion. .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*& -.cindex sorting a list +.cindex sorting "a list" .cindex list sorting +.cindex expansion "list sorting" After expansion, <&'string'&> is interpreted as a list, colon-separated by default, but the separator can be changed in the usual way. The <&'comparator'&> argument is interpreted as the operator @@ -13177,6 +13201,7 @@ listed in more than one group. .row &%message_logs%& "create per-message logs" .row &%preserve_message_logs%& "after message completion" .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&" +.row &%slow_lookup_log%& "control logging of slow DNS lookups" .row &%syslog_duplication%& "controls duplicate log lines on syslog" .row &%syslog_facility%& "set syslog &""facility""& field" .row &%syslog_processname%& "set syslog &""ident""& field" @@ -13290,6 +13315,7 @@ listed in more than one group. .row &%acl_smtp_mail%& "ACL for MAIL" .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command" .row &%acl_smtp_mime%& "ACL for MIME parts" +.row &%acl_smtp_notquit%& "ACL for non-QUIT terminations" .row &%acl_smtp_predata%& "ACL for start of data" .row &%acl_smtp_quit%& "ACL for QUIT" .row &%acl_smtp_rcpt%& "ACL for RCPT" @@ -13639,6 +13665,12 @@ This option is available when Exim is built with the content-scanning extension. It defines the ACL that is run for each MIME part in a message. See section &<>& for details. +.option acl_smtp_notquit main string&!! unset +.cindex "not-QUIT, ACL for" +This option defines the ACL that is run when an SMTP session +ends without a QUIT command being received. +See chapter &<>& for further details. + .option acl_smtp_predata main string&!! unset This option defines the ACL that is run when an SMTP DATA command is received, before the message itself is received. See chapter &<>& for @@ -14149,6 +14181,8 @@ servers have all been upgraded, there should be no need for this option. .option dns_retrans main time 0s .cindex "DNS" "resolver options" +.cindex timeout "dns lookup" +.cindex "DNS" timeout The options &%dns_retrans%& and &%dns_retry%& can be used to set the retransmission and retry parameters for DNS lookups. Values of zero (the defaults) leave the system default settings unchanged. The first value is the @@ -14158,6 +14192,7 @@ take. I haven't found any documentation about timeouts on DNS lookups; these parameter values are available in the external resolver interface structure, but nowhere does it seem to describe how they are used or what you might want to set in them. +See also the &%slow_lookup_log%& option. .option dns_retry main integer 0 @@ -15717,6 +15752,16 @@ it qualifies them only if the message came from a host that matches using TCP/IP), and the &%-bnq%& option was not set. +.option slow_lookup_log main integer 0 +.cindex "logging" "slow lookups" +.cindex "dns" "logging slow lookups" +This option controls logging of slow lookups. +If the value is nonzero it is taken as a number of milliseconds +and lookups taking longer than this are logged. +Currently this applies only to DNS lookups. + + + .option smtp_accept_keepalive main boolean true .cindex "keepalive" "on incoming connection" This option controls the setting of the SO_KEEPALIVE option on incoming @@ -17013,6 +17058,25 @@ or for any deliveries caused by this router. You should not set this option unless you really, really know what you are doing. See also the generic transport option of the same name. +.option dnssec_request_domains routers "domain list&!!" unset +.cindex "MX record" "security" +.cindex "DNSSEC" "MX lookup" +.cindex "security" "MX lookup" +.cindex "DNS" "DNSSEC" +DNS lookups for domains matching &%dnssec_request_domains%& will be done with +the dnssec request bit set. +This applies to all of the SRV, MX, AAAA, A lookup sequence. + +.option dnssec_require_domains routers "domain list&!!" unset +.cindex "MX record" "security" +.cindex "DNSSEC" "MX lookup" +.cindex "security" "MX lookup" +.cindex "DNS" "DNSSEC" +DNS lookups for domains matching &%dnssec_request_domains%& will be done with +the dnssec request bit set. Any returns not having the Authenticated Data bit +(AD bit) set will be ignored and logged as a host-lookup failure. +This applies to all of the SRV, MX, AAAA, A lookup sequence. + .option domains routers&!? "domain list&!!" unset .cindex "router" "restricting to specific domains" @@ -17984,6 +18048,9 @@ There are a few cases where a &(dnslookup)& router will decline to accept an address; if such a router is expected to handle "all remaining non-local domains", then it is important to set &%no_more%&. +The router will defer rather than decline if the domain +is found in the &%fail_defer_domains%& router option. + Reasons for a &(dnslookup)& router to decline currently include: .ilist The domain does not exist in DNS @@ -18062,27 +18129,16 @@ when there is a DNS lookup error. -.option dnssec_request_domains dnslookup "domain list&!!" unset -.cindex "MX record" "security" -.cindex "DNSSEC" "MX lookup" -.cindex "security" "MX lookup" -.cindex "DNS" "DNSSEC" -DNS lookups for domains matching &%dnssec_request_domains%& will be done with -the dnssec request bit set. -This applies to all of the SRV, MX A6, AAAA, A lookup sequence. - - - -.option dnssec_require_domains dnslookup "domain list&!!" unset -.cindex "MX record" "security" -.cindex "DNSSEC" "MX lookup" -.cindex "security" "MX lookup" -.cindex "DNS" "DNSSEC" -DNS lookups for domains matching &%dnssec_request_domains%& will be done with -the dnssec request bit set. Any returns not having the Authenticated Data bit -(AD bit) set wil be ignored and logged as a host-lookup failure. -This applies to all of the SRV, MX A6, AAAA, A lookup sequence. +.option fail_defer_domains dnslookup "domain list&!!" unset +.cindex "MX record" "not found" +DNS lookups for domains matching &%fail_defer_domains%& +which find no matching record will cause the router to defer +rather than the default behaviour of decline. +This maybe be useful for queueing messages for a newly created +domain while the DNS configuration is not ready. +However, it will result in any message with mistyped domains +also being queued. .option mx_domains dnslookup "domain list&!!" unset @@ -23008,7 +23064,7 @@ details. .cindex "DNS" "DNSSEC" DNS lookups for domains matching &%dnssec_request_domains%& will be done with the dnssec request bit set. -This applies to all of the SRV, MX A6, AAAA, A lookup sequence. +This applies to all of the SRV, MX, AAAA, A lookup sequence. @@ -23020,7 +23076,7 @@ This applies to all of the SRV, MX A6, AAAA, A lookup sequence. DNS lookups for domains matching &%dnssec_request_domains%& will be done with the dnssec request bit set. Any returns not having the Authenticated Data bit (AD bit) set wil be ignored and logged as a host-lookup failure. -This applies to all of the SRV, MX A6, AAAA, A lookup sequence. +This applies to all of the SRV, MX, AAAA, A lookup sequence. @@ -23171,12 +23227,13 @@ that matches this list, even if the server host advertises PIPELINING support. Exim will not try to start a TLS session when delivering to any host that matches this list. See chapter &<>& for details of TLS. -.option hosts_verify_avoid_tls smtp "host list&!!" * +.new +.option hosts_verify_avoid_tls smtp "host list&!!" unset .cindex "TLS" "avoiding for certain hosts" Exim will not try to start a TLS session for a verify callout, or when delivering in cutthrough mode, to any host that matches this list. -Note that the default is to not use TLS. +.wen .option hosts_max_try smtp integer 5 @@ -24355,6 +24412,13 @@ A server unexpectedly closed the SMTP connection. There may, of course, legitimate reasons for this (host died, network died), but if it repeats a lot for the same host, it indicates something odd. +.vitem &%lookup%& +A DNS lookup for a host failed. +Note that a &%dnslookup%& router will need to have matched +its &%fail_defer_domains%& option for this retry type to be usable. +Also note that a &%manualroute%& router will probably need +its &%host_find_failed%& option set to &%defer%&. + .vitem &%refused_MX%& A connection to a host obtained from an MX record was refused. @@ -27107,8 +27171,8 @@ the feature was not requested by the client. .cindex "QUIT, ACL for" The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL does not affect the response code to QUIT, which is always 221. Thus, the ACL -does not in fact control any access. For this reason, the only verbs that are -permitted are &%accept%& and &%warn%&. +does not in fact control any access. For this reason, it may only accept +or warn as its final result. This ACL can be used for tasks such as custom logging at the end of an SMTP session. For example, you can use ACL variables in other ACLs to count @@ -31133,7 +31197,8 @@ containing the decoded data. This is perhaps the most important of the MIME variables. It contains a proposed filename for an attachment, if one was found in either the &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be -RFC2047 decoded, but no additional sanity checks are done. If no filename was +RFC2047 or RFC2231 decoded, but no additional sanity checks are done. + If no filename was found, this variable contains the empty string. .vitem &$mime_is_coverletter$& @@ -35688,6 +35753,8 @@ search term. If the location of a &'zcat'& command is known from the definition of ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it. +If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use +autodetection of some well known compression extensions. .section "Selecting messages by various criteria (exipick)" "SECTexipick"