Previous: dns_query, Up: DNS functions [Contents][Index]
These functions are implemented in two layers: primitive built-in functions which raise exceptions if the lookup fails, and library calls that are warranted to always return meaningful value without throwing exceptions.
The built-in layer is always available. The library calls become available after requesting the dns module (see Modules):
require dns
Returns a whitespace-separated list of IP addresses (A
records) for domain.
Returns a whitespace-separated list of domain names (PTR
records) for the IPv4 address ipstr.
Returns a whitespace-separated list of ‘MX’ names (if ip is not
given or if it is 0
) or ‘MX’ IP addresses (if
ip!=0
)) for domain. Within the returned
string, items are sorted in order of increasing ‘MX’ priority.
If domain has no ‘MX’ records, an empty string is returned.
If the DNS query fails, getmx
raises an appropriate
exception.
Examples:
getmx("mafra.cz") ⇒ "smtp1.mafra.cz smtp2.mafra.cz relay.iol.cz" getmx("idnes.cz") ⇒ "smtp1.mafra.cz smtp2.mafra.cz relay.iol.cz" getmx("gnu.org") ⇒ "mx10.gnu.org mx20.gnu.org" getmx("org.pl") ⇒ ""
Notes:
getmx(domain)
can
differ from that obtained from getmx(domain, 1)
, e.g.:
getmx("aol.com") ⇒ mailin-01.mx.aol.com mailin-02.mx.aol.com mailin-03.mx.aol.com mailin-04.mx.aol.com getmx("aol.com", 1) ⇒ 64.12.137.89 64.12.137.168 64.12.137.184 64.12.137.249 64.12.138.57 64.12.138.88 64.12.138.120 64.12.138.185 205.188.155.89 205.188.156.185 205.188.156.249 205.188.157.25 205.188.157.217 205.188.158.121 205.188.159.57 205.188.159.217
dns_query
.
If you intend to iterate over returned values, better use
dns_query
directly, e.g. instead of doing
string_list_iterate(getmx(domain), ` ', MX, `do_something(MX)')
use
set n dns_query(DNS_TYPE_MX, domain) if n >= 0 loop for set i 0, while i < dns_reply_count(n), set i i + 1 do do_something(dns_reply_string(n, i)) done dns_reply_release(n) fi
See dns_query, for details about the dns_query
function and
associated dns_reply_*
calls.
It will most probably be removed in future releases, when array data types are implemented.
Returns true
if the domain name given by its argument
has any ‘MX’ records.
If the DNS query fails, this function throws failure
or
temp_failure
.
Returns true
if the domain name given by its argument
has any ‘MX’ records.
Otherwise, if domain has no ‘MX’s or if the DNS query fails,
hasmx
returns false
.
The ip argument should be a string representing an IP address in dotted-quad notation. The function returns the canonical name of the host with this IP address obtained from DNS lookup. For example
primitive_hostname (${client_addr})
returns the fully qualified domain name of the host represented by Sendmail variable ‘client_addr’.
If there is no ‘PTR’ record for ip, primitive_hostname
raises the exception e_not_found
.
If DNS query fails, the function raises failure
or
temp_failure
, depending on the character of the failure.
The ip argument should be a string representing an IP address in dotted-quad notation. The function returns the canonical name of the host with this IP address obtained from DNS lookup.
If there is no ‘PTR’ record for ip, or if the lookup fails, the function returns ip unchanged.
The previous mailfromd
versions used the following
paradigm to check if an IP address resolves:
if hostname(ip) != ip ...
The domain argument is any valid domain name, the host is a host name or IP address.
The function returns true
if host is one of the ‘MX’
records for the domain.
If domain has no ‘MX’ records, primitive_ismx
raises
exception e_not_found
.
If DNS query fails, the function raises failure
or
temp_failure
, depending on the character of the failure.
The domain argument is any valid domain name, the host is a host name or IP address.
The function returns true
if host is one of the ‘MX’
records for the domain. Otherwise it returns false
.
If domain has no ‘MX’ records, or if the DNS query fails, the
function returns false
.
Reverse of primitive_hostname
. The primitive_resolve
function
returns the IP address for the host name specified by its host
argument. If the SMTP session uses IPv4 protocol, ‘A’ record
is queried. It it uses IPv6, ‘AAAA’ record is queried. A
particular record type can be requested via optional family,
which can have one of the following values (defined in
status.mfl):
RESOLVE_DFL
Look for ‘A’ or ‘AAAA’, depending on the connection type. This is the default.
RESOLVE_IP4
Resolve to IPv4 addresses (‘A’ records).
RESOLVE_IP6
Resolve to IPv6 addresses (‘AAAA’ records).
If host has no records of the requested type, the function raises the
exception e_not_found
.
If DNS lookup fails, the function raises failure
or
temp_failure
, depending on the character of the failure.
Optional domain argument is deprecated. If a non-empty string is given as domain, the function works as follows:
The host must be a string representation of an IPv4 address in
dotted-quad form. If it is not, a e_inval
exception is thrown.
The octets in the IPv4 are reversed, a dot and ‘domain’ are
appended to it, and a ‘PTR’ record is queried for the resulting
name.
Thus, the call
primitive_resolve("192.0.2.1", "in-addr.arpa")
is equivalent to
primitive_hostname("192.0.2.1")
The host must be a string representation of an IPv6. If it is
not, a e_inval
exception is thrown. The octets of this IPv6
address are reversed, a dot and ‘domain’ are appended to it, and
a ‘PTR’ record is queried for the resulting name.
Thus, the call
primitive_resolve("2001:DB8::1", "ip6.arpa")
is equivalent to
primitive_hostname("2001:DB8::1")
The address is reversed as in (1), then a dot and ‘domain’ are appended to it. Finally, the DNS is queried for an ‘A’ record of the resulting name.
Thus,
primitive_resolve("192.0.2.1", "rev.example.com")
is equivalent to
primitive_resolve("1.2.0.192.rev.example.com")
The address is reversed as in (2), then a dot and ‘domain’ are appended to it. Finally, the DNS is queried for an ‘AAAA’ record of the resulting name.
primitive_hostname(‘host.domain’,'',resolve)
.
Reverse of hostname
. The resolve
function
returns IP address for the host name specified by host
argument. If the host name cannot be resolved, or a DNS failure
occurs, the function returns ‘"0"’.
This function is entirely equivalent to primitive_resolve
(see above), except that it never raises exceptions.
Tests whether the DNS reverse-mapping for ip exists and correctly points to a domain name within a particular domain.
First, it obtains all ‘PTR’ records for ip. Then, for each record returned, a look up for ‘A’ (or ‘AAAA’, if ip is an IPv6 address) records is performed and IP addresses of each record are compared against ip. The function returns true if a matching ‘A’ (or ‘AAAA’) record is found.
This function can raise the following exceptions:
e_not_found
Unable to resolve IP address or hostname.
e_failure
Fatal error while resolving.
e_temp_failure
Temporary error in DNS resolution.
e_too_many
Too many CNAME records (see CNAME chains).
Returns ‘True’ if the domain domain has at least one ‘NS’ record. Throws exception if DNS lookup fails.
Returns ‘True’ if the domain domain has at least one ‘NS’ record. Returns ‘False’ if there are no ‘NS’ records or if the DNS lookup fails.
Returns a whitespace-separated list of all the ‘NS’ records for the domain domain. Optional parameters resolve and sort control the formatting. If resolve is 0 (the default), the resulting string will contain IP addresses of the NS servers. If resolve is not 0, hostnames will be returned instead. If sort is 1, the returned items will be sorted.
If the DNS query fails, getns
raises an appropriate
exception.
Notes:
dns_query
.
If you intend to iterate over returned values, better use
dns_query
directly, e.g. instead of doing
string_list_iterate(getns(domain), ` ', NS, `do_something(NS)')
use
set n dns_query(DNS_TYPE_NS, domain) if n >= 0 loop for set i 0, while i < dns_reply_count(n), set i i + 1 do do_something(dns_reply_string(n, i)) done dns_reply_release(n) fi
See dns_query, for details about the dns_query
function and
associated dns_reply_*
calls.
It will most probably be removed in future releases, when array data types are implemented.
Previous: dns_query, Up: DNS functions [Contents][Index]