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cmd/derper: randomize IPs on refreshBootstrapDNS (#7440)

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This is to address a possible DNS failure on startup. Before this
change IPv6 addresses would be listed first, and the client dialer would
fail for hosts without IPv6 connectivity.
This commit is contained in:
shayne 2023-03-02 23:36:12 -05:00 committed by GitHub
parent 27575cd52d
commit d92ef4c215
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1 changed files with 8 additions and 0 deletions
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8
cmd/derper/bootstrap_dns.go
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@ -8,6 +8,7 @@ import (
"encoding/json" "encoding/json"
"expvar" "expvar"
"log" "log"
"math/rand"
"net" "net"
"net/http" "net/http"
"strings" "strings"
@ -52,6 +53,13 @@ func refreshBootstrapDNS() {
ctx, cancel := context.WithTimeout(context.Background(), refreshTimeout) ctx, cancel := context.WithTimeout(context.Background(), refreshTimeout)
defer cancel() defer cancel()
dnsEntries := resolveList(ctx, strings.Split(*bootstrapDNS, ",")) dnsEntries := resolveList(ctx, strings.Split(*bootstrapDNS, ","))
// Randomize the order of the IPs for each name to avoid the client biasing
// to IPv6
for k := range dnsEntries {
ips := dnsEntries[k]
rand.Shuffle(len(ips), func(i, j int) { ips[i], ips[j] = ips[j], ips[i] })
dnsEntries[k] = ips
}
j, err := json.MarshalIndent(dnsEntries, "", "\t") j, err := json.MarshalIndent(dnsEntries, "", "\t")
if err != nil { if err != nil {
// leave the old values in place // leave the old values in place