我一直在嘗試解決使用curl 查找命令需要很長時間（有時）而有時很快的問題。
TL;DR 問題：我如何進一步排除故障。
直接連接到 IP 位址沒有問題。
我嘗試過兩個不同的位置、多台機器（RPi、debian vm、Windows10）。
我嘗試將名稱伺服器設定為 1.1.1.1 和 8.8.8.8，但結果相同
我已經更改了 /etc/resolv.conf 以便它包含（是的。我已經對它進行了寫入保護）
options timeout:1
所以現在 dns_resolution 成功之前不再需要 5 秒。
對我來說，它首先看起來像是防火牆丟棄資料包問題或 ipv6-try 問題。但是我在機器上禁用了 ipv6，但沒有成功。
我使用這個命令來進行查找：
while :; do curl --max-time 10 -w "time_namelookup: %{time_namelookup}, time_connect: %{time_connect}, time_appconnect: %{time_appconnect}, time_pretransfer: %{time_pretransfer}, time_redirect: %{time_redirect}, time_starttransfer: %{time_starttransfer}, time_total: %{time_total}\n" -o /dev/null -s "https://www.google.com"; sleep 1; done
這是一些範例結果：
time_namelookup: 1.059151, time_connect: 1.083971, time_appconnect: 1.129219, time_pretransfer: 1.129803, time_redirect: 0.000000, time_starttransfer: 1.191138, time_total: 1.198772
time_namelookup: 1.058956, time_connect: 1.084363, time_appconnect: 1.130112, time_pretransfer: 1.131392, time_redirect: 0.000000, time_starttransfer: 1.291702, time_total: 1.300107
time_namelookup: 1.057719, time_connect: 1.083355, time_appconnect: 1.128083, time_pretransfer: 1.128726, time_redirect: 0.000000, time_starttransfer: 1.190859, time_total: 1.198635
time_namelookup: 0.018382, time_connect: 0.043042, time_appconnect: 0.077228, time_pretransfer: 0.077517, time_redirect: 0.000000, time_starttransfer: 0.142618, time_total: 0.150624
time_namelookup: 1.058276, time_connect: 1.082821, time_appconnect: 1.127496, time_pretransfer: 1.128083, time_redirect: 0.000000, time_starttransfer: 1.188930, time_total: 1.197614
time_namelookup: 0.023630, time_connect: 0.047877, time_appconnect: 0.079810, time_pretransfer: 0.080053, time_redirect: 0.000000, time_starttransfer: 0.136007, time_total: 0.141614
time_namelookup: 0.018607, time_connect: 0.043160, time_appconnect: 0.079620, time_pretransfer: 0.079966, time_redirect: 0.000000, time_starttransfer: 0.139617, time_total: 0.145728
time_namelookup: 1.059191, time_connect: 1.084436, time_appconnect: 1.127247, time_pretransfer: 1.127825, time_redirect: 0.000000, time_starttransfer: 1.189962, time_total: 1.199934
time_namelookup: 1.058040, time_connect: 1.083303, time_appconnect: 1.127172, time_pretransfer: 1.128314, time_redirect: 0.000000, time_starttransfer: 1.194481, time_total: 1.202276
time_namelookup: 0.018539, time_connect: 0.043664, time_appconnect: 0.079772, time_pretransfer: 0.080074, time_redirect: 0.000000, time_starttransfer: 0.141406, time_total: 0.147358
time_namelookup: 1.060180, time_connect: 1.084996, time_appconnect: 1.130302, time_pretransfer: 1.131054, time_redirect: 0.000000, time_starttransfer: 1.197778, time_total: 1.205363
time_namelookup: 0.031891, time_connect: 0.058458, time_appconnect: 0.097752, time_pretransfer: 0.098055, time_redirect: 0.000000, time_starttransfer: 0.157533, time_total: 0.188634
time_namelookup: 1.059059, time_connect: 1.083472, time_appconnect: 1.126565, time_pretransfer: 1.127196, time_redirect: 0.000000, time_starttransfer: 1.189149, time_total: 1.195730
time_namelookup: 0.023647, time_connect: 0.048197, time_appconnect: 0.082277, time_pretransfer: 0.082772, time_redirect: 0.000000, time_starttransfer: 0.143120, time_total: 0.149757
time_namelookup: 0.017073, time_connect: 0.041658, time_appconnect: 0.081927, time_pretransfer: 0.082310, time_redirect: 0.000000, time_starttransfer: 0.144873, time_total: 0.152739
time_namelookup: 0.017251, time_connect: 0.042056, time_appconnect: 0.079905, time_pretransfer: 0.080475, time_redirect: 0.000000, time_starttransfer: 0.141332, time_total: 0.147886
然而，執行 dig 命令非常快：
$ dig @dns.google google.com
; <<>> DiG 9.11.5-P4-5.1+deb10u8-Raspbian <<>> @dns.google google.com
; (2 servers found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 13497
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;google.com. IN A
;; ANSWER SECTION:
google.com. 221 IN A 172.217.19.78
;; Query time: 25 msec
;; SERVER: 8.8.4.4#53(8.8.4.4)
;; WHEN: Thu Feb 16 10:44:24 UTC 2023
;; MSG SIZE rcvd: 55
$ dig @1.1.1.1 google.com
; <<>> DiG 9.11.5-P4-5.1+deb10u8-Raspbian <<>> @1.1.1.1 google.com
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 54885
;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;google.com. IN A
;; ANSWER SECTION:
google.com. 65 IN A 142.250.147.101
google.com. 65 IN A 142.250.147.113
google.com. 65 IN A 142.250.147.138
google.com. 65 IN A 142.250.147.139
google.com. 65 IN A 142.250.147.100
google.com. 65 IN A 142.250.147.102
;; Query time: 13 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Thu Feb 16 10:44:33 UTC 2023
;; MSG SIZE rcvd: 135
從丹麥發出的多個網路連線傳出的情況類似
我還發現一些根本沒有問題的發現。一台設備上的 dns 解析速度很快，而另一台運行相同 ASN-no 但不同子 IP 範圍的設備則出現問題。
MTR/traceroute 沒有顯示任何問題的跡象。我只是不確定為什麼它會轉到 100.xxx ip 位址，但一定有某種路由。其他連線上不會發生這種情況
My traceroute [v0.92]
devicename (xx.x.x.xxx) 2023-02-16T11:50:47+0000
Keys: Help Display mode Restart statistics Order of fields quit
Packets Pings
Host Loss% Snt Last Avg Best Wrst StDev
1. xx.x.x.x 0.0% 211 3.0 2.2 1.4 8.3 0.8
2. 31.3.xx.xxx 0.0% 211 1.7 2.1 1.4 7.3 0.7
3. 100.64.x.xxx 0.0% 211 6.8 8.1 6.1 37.8 3.5
4. 94.127.48.17 1.4% 211 7.4 8.3 6.1 48.0 6.3
5. xe-2-1-0-311.alb2nqe10.d 0.0% 211 6.9 9.4 6.3 46.4 6.3
6. ae0-0.stkm2nqp7.se.ip.td 0.0% 211 15.7 16.4 14.8 35.1 2.8
7. 72.14.214.162 0.0% 211 17.4 17.1 15.3 33.4 2.7
8. 209.85.254.3 0.0% 211 16.1 17.0 15.4 48.7 3.8
9. 108.170.253.181 0.9% 211 18.4 17.8 15.2 60.1 6.2
10. 108.170.227.249 10.0% 211 20.6 17.8 15.4 41.2 4.2
209.85.246.61
11. 142.251.51.215 2.8% 211 26.7 26.4 24.0 54.7 4.6
209.85.248.7
12. 142.250.214.184 1.4% 210 44.6 25.9 23.7 48.6 4.1
142.251.239.219
13. 172.253.70.203 0.5% 210 25.1 24.8 23.9 28.2 0.6
142.250.46.23
14. ???
15. ???
16. ???
17. ???
18. ???
19. ???
20. ???
21. ???
22. ???
23. rd-in-f139.1e100.net 38.3% 210 24.8 25.0 24.1 30.7 0.7
Traceroute 顯示它先轉到一個實際的 IP 位址，然後轉到一個虛假的 (100.xxx) IP 位址。
traceroute to google.com (142.250.147.102), 30 hops max, 60 byte packets
1 xx.x.x.x (xx.x.x.x) 2.436 ms 2.624 ms 2.510 ms
2 31.3.xx.xxx (31.3.xx.xxx) 2.392 ms 2.941 ms 2.834 ms
3 100.64.x.xxx (100.64.x.xxx) 6.451 ms 6.629 ms 6.519 ms
4 94.127.48.17 (94.127.48.17) 6.403 ms 6.600 ms 6.762 ms
5 xe-2-1-0-311.alb2nqe10.dk.ip.tdc.net (87.48.169.225) 6.653 ms 8.382 ms 8.074 ms
6 ae0-0.stkm2nqp7.se.ip.tdc.net (83.88.2.128) 16.956 ms 16.121 ms 15.401 ms
7 72.14.214.162 (72.14.214.162) 16.827 ms 16.741 ms 16.650 ms
8 * * *
9 108.170.254.33 (108.170.254.33) 17.564 ms 209.85.242.10 (209.85.242.10) 16.346 ms 108.170.253.161 (108.170.253.161) 17.412 ms
10 108.170.254.38 (108.170.254.38) 17.255 ms 108.170.253.182 (108.170.253.182) 17.105 ms 108.170.254.54 (108.170.254.54) 16.645 ms
11 209.85.246.61 (209.85.246.61) 16.484 ms 72.14.234.107 (72.14.234.107) 17.352 ms 142.250.235.228 (142.250.235.228) 17.045 ms
12 108.170.236.41 (108.170.236.41) 26.269 ms 26.088 ms 142.251.51.217 (142.251.51.217) 26.110 ms
13 142.251.239.219 (142.251.239.219) 24.352 ms 142.250.214.198 (142.250.214.198) 26.021 ms 142.250.214.178 (142.250.214.178) 26.295 ms
14 142.250.214.229 (142.250.214.229) 25.056 ms 142.250.215.9 (142.250.215.9) 25.494 ms 142.250.229.93 (142.250.229.93) 25.310 ms
15 * * *
16 * * *
17 * * *
18 * * *
19 * * *
20 * * *
21 * * *
22 * * *
23 * rd-in-f102.1e100.net (142.250.147.102) 25.956 ms *
答案1
假設輸出「dig」僅發出一個 A 請求（即一個 dns 請求），並且存在 ipv4 模式下的 mtr 及其 RTT 時間。假設在使用curl 的情況下，有兩個dns 請求：針對ipv4 和針對ipv6（A 和AAAA）。您是否嘗試過使用“-4”選項運行該curl範例來比較其僅用於ipv4解析的“time_namelookup”？