diff options
| author | Jeremy Harris <jgh146exb@wizmail.org> | 2015-09-17 13:35:16 +0100 |
|---|---|---|
| committer | Jeremy Harris <jgh146exb@wizmail.org> | 2015-09-17 13:35:16 +0100 |
| commit | 14b3c5bc64a16df07583fe4b5ef2e0129d063893 (patch) | |
| tree | 76f33f84acdf7e5af636dbea346da58e1cb09cc0 /doc | |
| parent | f64fbe039033d51be277431ce09fabd3ebbc7e74 (diff) | |
DNS: time-limit cached returns, using TTL. Bug 1395
This can matter for fast-changing data such as DNSBLs.
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/doc-docbook/spec.xfpt | 19 | ||||
| -rw-r--r-- | doc/doc-txt/ChangeLog | 3 |
2 files changed, 20 insertions, 2 deletions
diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 34fbed88f..ed3533a0c 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -6993,6 +6993,15 @@ 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%&. +.new +.cindex cacheing "of dns lookup" +.cindex TTL "of dns lookup" +.cindex DNS TTL +Dnsdb lookup results are cached within a single process (and its children). +The cache entry lifetime is limited to the smallest time-to-live (TTL) +value of the set of returned DNS records. +.wen + .section "Pseudo dnsdb record types" "SECID66" .cindex "MX record" "in &(dnsdb)& lookup" @@ -29208,9 +29217,15 @@ deny dnslists = blackholes.mail-abuse.org warn message = X-Warn: sending host is on dialups list dnslists = dialups.mail-abuse.org .endd -DNS list lookups are cached by Exim for the duration of the SMTP session, +.cindex cacheing "of dns lookup" +.cindex DNS TTL +DNS list lookups are cached by Exim for the duration of the SMTP session +.new +(but limited by the DNS return TTL value), +.wen so a lookup based on the IP address is done at most once for any incoming -connection. Exim does not share information between multiple incoming +connection (assuming long-enough TTL). +Exim does not share information between multiple incoming connections (but your local name server cache should be active). diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog index 969f1e3a7..37d66617e 100644 --- a/doc/doc-txt/ChangeLog +++ b/doc/doc-txt/ChangeLog @@ -46,6 +46,9 @@ JH/05 Downgrade message for a TLS-certificate-based authentication fail from HS/02 Add the Exim version string to the process info. This way exiwhat gives some more detail about the running daemon. +JH/06 Bug 1395: time-limit cacheing of DNS lookups, to the TTL value. This may + matter for fast-change records such as DNSBLs. + Exim version 4.86 ----------------- |