/
dns.go
executable file
·81 lines (65 loc) · 1.89 KB
/
dns.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
package node
import (
"fmt"
"strings"
config "github.com/fgeth/fg-ipfs-config"
doh "github.com/libp2p/go-doh-resolver"
madns "github.com/multiformats/go-multiaddr-dns"
"github.com/miekg/dns"
)
var defaultResolvers = map[string]string{
"eth.": "https://resolver.cloudflare-eth.com/dns-query",
"crypto.": "https://resolver.cloudflare-eth.com/dns-query",
}
func newResolver(url string) (madns.BasicResolver, error) {
if !strings.HasPrefix(url, "https://") {
return nil, fmt.Errorf("invalid resolver url: %s", url)
}
return doh.NewResolver(url), nil
}
func DNSResolver(cfg *config.Config) (*madns.Resolver, error) {
var opts []madns.Option
var err error
domains := make(map[string]struct{}) // to track overriden default resolvers
rslvrs := make(map[string]madns.BasicResolver) // to reuse resolvers for the same URL
for domain, url := range cfg.DNS.Resolvers {
if domain != "." && !dns.IsFqdn(domain) {
return nil, fmt.Errorf("invalid domain %s; must be FQDN", domain)
}
domains[domain] = struct{}{}
if url == "" {
// allow overriding of implicit defaults with the default resolver
continue
}
rslv, ok := rslvrs[url]
if !ok {
rslv, err = newResolver(url)
if err != nil {
return nil, fmt.Errorf("bad resolver for %s: %w", domain, err)
}
rslvrs[url] = rslv
}
if domain != "." {
opts = append(opts, madns.WithDomainResolver(domain, rslv))
} else {
opts = append(opts, madns.WithDefaultResolver(rslv))
}
}
// fill in defaults if not overriden by the user
for domain, url := range defaultResolvers {
_, ok := domains[domain]
if ok {
continue
}
rslv, ok := rslvrs[url]
if !ok {
rslv, err = newResolver(url)
if err != nil {
return nil, fmt.Errorf("bad resolver for %s: %w", domain, err)
}
rslvrs[url] = rslv
}
opts = append(opts, madns.WithDomainResolver(domain, rslv))
}
return madns.NewResolver(opts...)
}