Das beschriebene Path-MTU-Problem ist an meinem Internetanschluss über das Fernsehkabelnetzwerk (EuroDOCSIS) von UPC/Sunrise, mit Bridge-Modus, nicht reproduzierbar:
$ ping -c 10 -M do -s 1472 9.9.9.9
PING 9.9.9.9 (9.9.9.9) 1472(1500) Bytes Daten.
1480 Bytes von 9.9.9.9: icmp_seq=1 ttl=56 Zeit=18.1 ms
1480 Bytes von 9.9.9.9: icmp_seq=2 ttl=56 Zeit=20.8 ms
1480 Bytes von 9.9.9.9: icmp_seq=3 ttl=56 Zeit=18.1 ms
1480 Bytes von 9.9.9.9: icmp_seq=4 ttl=56 Zeit=19.6 ms
1480 Bytes von 9.9.9.9: icmp_seq=5 ttl=56 Zeit=17.0 ms
1480 Bytes von 9.9.9.9: icmp_seq=6 ttl=56 Zeit=16.5 ms
1480 Bytes von 9.9.9.9: icmp_seq=7 ttl=56 Zeit=25.0 ms
1480 Bytes von 9.9.9.9: icmp_seq=8 ttl=56 Zeit=16.0 ms
1480 Bytes von 9.9.9.9: icmp_seq=9 ttl=56 Zeit=20.3 ms
1480 Bytes von 9.9.9.9: icmp_seq=10 ttl=56 Zeit=18.3 ms
--- 9.9.9.9 ping-Statistik ---
10 Pakete übertragen, 10 empfangen, 0% Paketverlust, Zeit 9012ms
rtt min/avg/max/mdev = 15.971/18.952/25.034/2.511 ms
Offenbar sind die Path-MTU-Probleme hausgemacht, sprich im eigenen Heimnetzwerk zu suchen und die Fehlkonfiguration zu beheben.
Und an meinem Internetanschluss funktioniert die mit TLS-verschlüsselte Kommunikation auf die IP-Adresse 9.9.9.9 per Serverport TCP 443 (HTTPS):
$ openssl s_client -connect 9.9.9.9:443
CONNECTED(00000003)
Can't use SSL_get_servername
depth=2 C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert Global Root G3
verify return:1
depth=1 C = US, O = DigiCert Inc, CN = DigiCert Global G3 TLS ECC SHA384 2020 CA1
verify return:1
depth=0 C = CH, ST = Zurich, L = Zurich, O = Quad9, CN = dns.quad9.net
verify return:1
---
Certificate chain
0 s:C = CH, ST = Zurich, L = Zurich, O = Quad9, CN = dns.quad9.net
i:C = US, O = DigiCert Inc, CN = DigiCert Global G3 TLS ECC SHA384 2020 CA1
a:PKEY: id-ecPublicKey, 256 (bit); sigalg: ecdsa-with-SHA384
v:NotBefore: Jul 17 00:00:00 2024 GMT; NotAfter: Jul 16 23:59:59 2025 GMT
1 s:C = US, O = DigiCert Inc, CN = DigiCert Global G3 TLS ECC SHA384 2020 CA1
i:C = US, O = DigiCert Inc, OU = www.digicert.com, CN = DigiCert Global Root G3
a:PKEY: id-ecPublicKey, 384 (bit); sigalg: ecdsa-with-SHA384
v:NotBefore: Apr 14 00:00:00 2021 GMT; NotAfter: Apr 13 23:59:59 2031 GMT
---
Server certificate
-----BEGIN CERTIFICATE-----
....
-----END CERTIFICATE-----
subject=C = CH, ST = Zurich, L = Zurich, O = Quad9, CN = dns.quad9.net
issuer=C = US, O = DigiCert Inc, CN = DigiCert Global G3 TLS ECC SHA384 2020 CA1
---
No client certificate CA names sent
Peer signing digest: SHA256
Peer signature type: ECDSA
Server Temp Key: X25519, 253 bits
---
SSL handshake has read 3272 bytes and written 375 bytes
Verification: OK
---
New, TLSv1.3, Cipher is TLS_AES_256_GCM_SHA384
Server public key is 256 bit
This TLS version forbids renegotiation.
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 0 (ok)
---
---
Post-Handshake New Session Ticket arrived:
SSL-Session:
Protocol : TLSv1.3
Cipher : TLS_AES_256_GCM_SHA384
Session-ID: D0345610745AD00F62E45EA2BAA095C1E9F702CEF5874328CB1F63B575262ECF
Session-ID-ctx:
Resumption PSK: 69A80B8C500BF15B5949D21807322335076F6C0B14A12BB93D8AF42A4DE55D9D240C5A945E4CFCA336EE6A1DFA3DF228
PSK identity: None
PSK identity hint: None
SRP username: None
TLS session ticket lifetime hint: 7200 (seconds)
TLS session ticket:
0000 - 79 94 6a b2 0d 2c a5 67-f9 af 08 21 07 96 07 85 y.j..,.g...!....
0010 - 30 dc fb 45 15 5b aa d9-5c 51 0f 41 a6 bc d0 77 0..E.[..\Q.A...w
0020 - ed 55 fe dd 2c 85 de 6d-bd a2 8d a7 cf 74 28 f6 .U..,..m.....t(.
0030 - 5e 11 75 04 77 3c b1 b0-c0 ce cc a3 46 59 12 44 ^.u.w<......FY.D
0040 - 94 32 3b ea 63 d9 f7 ae-1e 0f 66 25 69 90 46 e7 .2;.c.....f%i.F.
0050 - dd 56 6c 80 8a bb 16 41-62 7b 27 c4 30 2e 9a a9 .Vl....Ab{'.0...
0060 - bc e9 ac b4 30 4e 7f 21-b9 02 5b 45 4d c7 f5 89 ....0N.!..[EM...
0070 - fa d8 32 6e f2 65 4c ca-61 a9 08 26 f9 b6 8c a2 ..2n.eL.a..&....
0080 - b0 31 9f 86 55 6d ee a1-8d 8d b5 27 71 a5 46 da .1..Um.....'q.F.
0090 - 0c eb ad d8 42 40 a4 2a-d1 c7 9b 96 6b 03 2f 10 ....B@.*....k./.
00a0 - c5 41 d1 0c 0f d0 af 12-f1 0f 08 a0 a1 31 a3 fc .A...........1..
00b0 - 04 31 1a 06 fd f7 16 12-44 8d a2 99 3b 9e 1d a2 .1......D...;...
Start Time: 1738267010
Timeout : 7200 (sec)
Verify return code: 0 (ok)
Extended master secret: no
Max Early Data: 0
---
read R BLOCK
---
Post-Handshake New Session Ticket arrived:
SSL-Session:
Protocol : TLSv1.3
Cipher : TLS_AES_256_GCM_SHA384
Session-ID: F7D2E5AAEA77AB961453B040FE7A700BE35D84CC01980C8F79B31415EEB691FB
Session-ID-ctx:
Resumption PSK: 12DA273F752563C8F352118509BD93DFAEF8C157AA56DFD46539637FD8EB5141374E7AE6DADC982D415F51E5ACC2EEF2
PSK identity: None
PSK identity hint: None
SRP username: None
TLS session ticket lifetime hint: 7200 (seconds)
TLS session ticket:
0000 - 79 94 6a b2 0d 2c a5 67-f9 af 08 21 07 96 07 85 y.j..,.g...!....
0010 - 1d ca c4 50 bd 74 8a 89-b7 f0 04 b6 b4 65 bd 5f ...P.t.......e._
0020 - 76 17 f3 31 9a a6 b9 76-9f ab 63 37 f6 59 c2 36 v..1...v..c7.Y.6
0030 - 15 e2 21 83 60 63 e5 2c-33 5f b3 83 39 62 bb e6 ..!.`c.,3_..9b..
0040 - 1a 08 a3 c0 7f 94 04 34-83 57 8c 46 52 47 9e 6a .......4.W.FRG.j
0050 - d5 4f d3 b0 6d 46 9b ea-34 de 51 cd d2 c0 5c 5b .O..mF..4.Q...\[
0060 - 4e 55 f0 1c 4a 66 f0 9b-1d 28 8f da 51 92 4e c3 NU..Jf...(..Q.N.
0070 - 37 ff e0 b8 aa 1b bc 02-4b e9 29 d6 f8 ca f2 c2 7.......K.).....
0080 - 5a b4 2b 55 20 60 d7 fb-d9 e1 40 d7 a2 6a 20 80 Z.+U `....@..j .
0090 - 78 7f 6a 46 8e c6 3a a2-e1 36 21 c0 45 ab e5 31 x.jF..:..6!.E..1
00a0 - a8 24 86 ce a7 dd 63 f8-1a a7 2c 9d 48 cb 27 dd .$....c...,.H.'.
00b0 - 80 72 be 10 86 5a 02 20-8f d1 73 d4 fd 9f 9e 4a .r...Z. ..s....J
Start Time: 1738267010
Timeout : 7200 (sec)
Verify return code: 0 (ok)
Extended master secret: no
Max Early Data: 0
---
read R BLOCK