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feat: host collector for DNS (#1617)
* add struct for host dns collector * add miekg/dns * add more logs * nit * new field names * use Hostnames instead of Names * misc update * make schemas * no error when there is no resolv.conf * query all searches * add summary.json file * merge summary into result file * query AAAA and CNAME as well * update schema for hostnames to be required
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,205 @@ | ||
| package collect | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "encoding/json" | ||
| "fmt" | ||
| "os" | ||
| "path/filepath" | ||
| "strings" | ||
|
|
||
| "github.com/miekg/dns" | ||
| "github.com/pkg/errors" | ||
| "github.com/replicatedhq/troubleshoot/internal/util" | ||
| troubleshootv1beta2 "github.com/replicatedhq/troubleshoot/pkg/apis/troubleshoot/v1beta2" | ||
| "k8s.io/klog/v2" | ||
| ) | ||
|
|
||
| type CollectHostDNS struct { | ||
| hostCollector *troubleshootv1beta2.HostDNS | ||
| BundlePath string | ||
| } | ||
|
|
||
| type DNSResult struct { | ||
| Query DNSQuery `json:"query"` | ||
| ResolvedFromSearch string `json:"resolvedFromSearch"` | ||
| } | ||
|
|
||
| type DNSQuery map[string][]DNSEntry | ||
|
|
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| type DNSEntry struct { | ||
| Server string `json:"server"` | ||
| Search string `json:"search"` | ||
| Name string `json:"name"` | ||
| Answer string `json:"answer"` | ||
| Record string `json:"record"` | ||
| } | ||
|
|
||
| const ( | ||
| HostDNSPath = "host-collectors/dns/" | ||
| resolvConf = "/etc/resolv.conf" | ||
| ) | ||
|
|
||
| func (c *CollectHostDNS) Title() string { | ||
| return hostCollectorTitleOrDefault(c.hostCollector.HostCollectorMeta, "dns") | ||
| } | ||
|
|
||
| func (c *CollectHostDNS) IsExcluded() (bool, error) { | ||
| return isExcluded(c.hostCollector.Exclude) | ||
| } | ||
|
|
||
| func (c *CollectHostDNS) Collect(progressChan chan<- interface{}) (map[string][]byte, error) { | ||
|
|
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| names := c.hostCollector.Hostnames | ||
| if len(names) == 0 { | ||
| return nil, errors.New("hostnames is required") | ||
| } | ||
|
|
||
| // first, get DNS config from /etc/resolv.conf | ||
| dnsConfig, err := getDNSConfig() | ||
| if err != nil { | ||
| return nil, errors.Wrap(err, "failed to read DNS resolve config") | ||
| } | ||
|
|
||
| // query DNS for each name | ||
| dnsEntries := make(map[string][]DNSEntry) | ||
| dnsResult := DNSResult{Query: dnsEntries} | ||
| allResolvedSearches := []string{} | ||
|
|
||
| for _, name := range names { | ||
| entries, resolvedSearches, err := resolveName(name, dnsConfig) | ||
| if err != nil { | ||
| klog.V(2).Infof("Failed to resolve name %s: %v", name, err) | ||
| } | ||
| dnsEntries[name] = entries | ||
| allResolvedSearches = append(allResolvedSearches, resolvedSearches...) | ||
| } | ||
|
|
||
| // deduplicate resolved searches | ||
| dnsResult.ResolvedFromSearch = strings.Join(util.Dedup(allResolvedSearches), ", ") | ||
|
|
||
| // convert dnsResult to a JSON string | ||
| dnsResultJSON, err := json.MarshalIndent(dnsResult, "", " ") | ||
| if err != nil { | ||
| return nil, errors.Wrap(err, "failed to marshal DNS query result to JSON") | ||
| } | ||
|
|
||
| output := NewResult() | ||
| outputFile := c.getOutputFilePath("result.json") | ||
| output.SaveResult(c.BundlePath, outputFile, bytes.NewBuffer(dnsResultJSON)) | ||
|
|
||
| // write /etc/resolv.conf to a file | ||
| resolvConfData, err := getResolvConf() | ||
| if err != nil { | ||
| klog.V(2).Infof("failed to read DNS resolve config: %v", err) | ||
| } else { | ||
| outputFile = c.getOutputFilePath("resolv.conf") | ||
| output.SaveResult(c.BundlePath, outputFile, bytes.NewBuffer(resolvConfData)) | ||
| } | ||
|
|
||
| return output, nil | ||
| } | ||
|
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| func (c *CollectHostDNS) getOutputFilePath(name string) string { | ||
| // normalize title to be used as a directory name, replace spaces with underscores | ||
| title := strings.ReplaceAll(c.Title(), " ", "_") | ||
| return filepath.Join(HostDNSPath, title, name) | ||
| } | ||
|
|
||
| func getDNSConfig() (*dns.ClientConfig, error) { | ||
| file, err := os.Open(resolvConf) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| defer file.Close() | ||
|
|
||
| config, err := dns.ClientConfigFromFile(file.Name()) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("failed to parse resolv.conf: %v", err) | ||
| } | ||
|
|
||
| return config, nil | ||
| } | ||
|
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| func resolveName(name string, config *dns.ClientConfig) ([]DNSEntry, []string, error) { | ||
|
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| results := []DNSEntry{} | ||
| resolvedSearches := []string{} | ||
|
|
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| // get a name list based on the config | ||
| queryList := config.NameList(name) | ||
| klog.V(2).Infof("DNS query list: %v", queryList) | ||
|
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| // for each name in the list, query all the servers | ||
| // we will query all search domains for each name | ||
| for _, query := range queryList { | ||
| for _, server := range config.Servers { | ||
| klog.V(2).Infof("Querying DNS server %s for name %s", server, query) | ||
|
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| entry := queryDNS(name, query, server+":"+config.Port) | ||
| results = append(results, entry) | ||
|
|
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| if entry.Search != "" { | ||
| resolvedSearches = append(resolvedSearches, entry.Search) | ||
| } | ||
| } | ||
| } | ||
| return results, resolvedSearches, nil | ||
| } | ||
|
|
||
| func getResolvConf() ([]byte, error) { | ||
| data, err := os.ReadFile(resolvConf) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return data, nil | ||
| } | ||
|
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||
| func queryDNS(name, query, server string) DNSEntry { | ||
| recordTypes := []uint16{dns.TypeA, dns.TypeAAAA, dns.TypeCNAME} | ||
| entry := DNSEntry{Name: query, Server: server, Answer: ""} | ||
|
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| for _, rec := range recordTypes { | ||
| m := &dns.Msg{} | ||
| m.SetQuestion(dns.Fqdn(query), rec) | ||
| in, err := dns.Exchange(m, server) | ||
|
|
||
| if err != nil { | ||
| klog.Errorf("failed to query DNS server %s for name %s: %v", server, query, err) | ||
| continue | ||
| } | ||
|
|
||
| if len(in.Answer) == 0 { | ||
| continue | ||
| } | ||
|
|
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| entry.Answer = in.Answer[0].String() | ||
|
|
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| // remember the search domain that resolved the query | ||
| // e.g. foo.test.com -> test.com | ||
| entry.Search = strings.Replace(query, name, "", 1) | ||
|
|
||
| // populate record detail | ||
| switch rec { | ||
| case dns.TypeA: | ||
| record, ok := in.Answer[0].(*dns.A) | ||
| if ok { | ||
| entry.Record = record.A.String() | ||
| } | ||
| case dns.TypeAAAA: | ||
| record, ok := in.Answer[0].(*dns.AAAA) | ||
| if ok { | ||
| entry.Record = record.AAAA.String() | ||
| } | ||
| case dns.TypeCNAME: | ||
| record, ok := in.Answer[0].(*dns.CNAME) | ||
| if ok { | ||
| entry.Record = record.Target | ||
| } | ||
| } | ||
|
|
||
| // break on the first successful query | ||
| break | ||
| } | ||
| return entry | ||
| } |
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