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add more documentation, examples with tests to illustrate reusable components

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This commit is contained in:
Mechiel Lukkien
2023-12-12 15:47:26 +01:00
parent 810cbdc61d
commit d1b66035a9
40 changed files with 973 additions and 119 deletions
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15
dnsbl/dnsbl.go
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@ -1,4 +1,17 @@
// Package dnsbl implements DNS block lists (RFC 5782), for checking incoming messages from sources without reputation.
//
// A DNS block list contains IP addresses that should be blocked. The DNSBL is
// queried using DNS "A" lookups. The DNSBL starts at a "zone", e.g.
// "dnsbl.example". To look up whether an IP address is listed, a DNS name is
// composed: For 10.11.12.13, that name would be "13.12.11.10.dnsbl.example". If
// the lookup returns "record does not exist", the IP is not listed. If an IP
// address is returned, the IP is listed. If an IP is listed, an additional TXT
// lookup is done for more information about the block. IPv6 addresses are also
// looked up with an DNS "A" lookup of a name similar to an IPv4 address, but with
// 4-bit hexadecimal dot-separated characters, in reverse.
//
// The health of a DNSBL "zone" can be check through a lookup of 127.0.0.1
// (must not be present) and 127.0.0.2 (must be present).
package dnsbl
import (
@ -21,7 +34,7 @@ var (
MetricLookup stub.HistogramVec = stub.HistogramVecIgnore{}
)
var ErrDNS = errors.New("dnsbl: dns error")
var ErrDNS = errors.New("dnsbl: dns error") // Temporary error.
// Status is the result of a DNSBL lookup.
type Status string

31
dnsbl/examples_test.go Normal file
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@ -0,0 +1,31 @@
package dnsbl_test
import (
"context"
"log"
"net"
"golang.org/x/exp/slog"
"github.com/mjl-/mox/dns"
"github.com/mjl-/mox/dnsbl"
)
func ExampleLookup() {
ctx := context.Background()
resolver := dns.StrictResolver{}
// Lookup if ip 127.0.0.2 is in spamhaus blocklist at zone sbl.spamhaus.org.
status, explanation, err := dnsbl.Lookup(ctx, slog.Default(), resolver, dns.Domain{ASCII: "sbl.spamhaus.org"}, net.ParseIP("127.0.0.2"))
if err != nil {
log.Fatalf("dnsbl lookup: %v", err)
}
switch status {
case dnsbl.StatusTemperr:
log.Printf("dnsbl lookup, temporary dns error: %v", err)
case dnsbl.StatusPass:
log.Printf("dnsbl lookup, ip not listed")
case dnsbl.StatusFail:
log.Printf("dnsbl lookup, ip listed: %s", explanation)
}
}