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Dun Apprentice
Joined: 17 Apr 2004 Posts: 172 Location: Amsterdam (NL) / Venice (IT)
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Posted: Thu Mar 30, 2006 2:36 pm Post subject: PPTPClient VS MS VPN Client. Problema MTU? [risolto ?!] |
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Salve a tutti. Ho un piccolo problemino di vpn...credo si tratti di mtu anche se non mi spiego un certo comportamento.
Ho configurato sul server il demone poptop per far da vpn server col seguente file di cfg:
Code: |
name pptpd
refuse-pap
refuse-chap
refuse-mschap
require-mschap-v2
mppe required,stateless
lock
nobsdcomp
nologfd
nodefaultroute
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Il client pptp invece e' configurato nel modo seguente:
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lock
noauth
nobsdcomp
nodeflate
mppe required,stateless
mtu 1400
mru 1400
lcp-echo-failure 10
lcp-echo-interval 10
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Il file peers e' invece:
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pty "pptp server_ip --nolaunchpppd"
name username
require-mschap-v2
remotename name
file /etc/ppp/options.name
ipparam name
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Il problema sorge quando faccio altro oltre che ai ping. Sul client cominciano ad apparire errori come testimonia ifconfig:
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ppp0 Link encap:Point-to-Point Protocol
inet addr:192.168.3.234 P-t-P:192.168.3.1 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1400 Metric:1
RX packets:56 errors:17 dropped:0 overruns:0 frame:0
TX packets:40 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:3
RX bytes:29207 (28.5 Kb) TX bytes:2039 (1.9 Kb)
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La cosa strana e' come da lato server non si abbiano invece avvisaglie di errori:
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gattaca ~ # ifconfig ppp0
ppp0 Link encap:Point-to-Point Protocol
inet addr:192.168.3.1 P-t-P:192.168.3.234 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1400 Metric:1
RX packets:130 errors:0 dropped:0 overruns:0 frame:0
TX packets:191 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:3
RX bytes:9945 (9.7 Kb) TX bytes:110448 (107.8 Kb)
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I ping pero' d'altro canto procedono senza errori fino a che la dimensioni dei pacchetti rimangono dentro l MTU.
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Ansia peers # ping -c 3 server_ip
PING server_ip (192.168.3.1) 56(84) bytes of data.
64 bytes from 192.168.3.1: icmp_seq=1 ttl=64 time=91.4 ms
64 bytes from 192.168.3.1: icmp_seq=2 ttl=64 time=91.7 ms
64 bytes from 192.168.3.1: icmp_seq=3 ttl=64 time=90.6 ms
--- server_ip ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2001ms
rtt min/avg/max/mdev = 90.652/91.273/91.755/0.578 ms
Ansia peers # ping -c 3 -s 1300 server_ip
PING server_ip (192.168.3.1) 1300(1328) bytes of data.
1308 bytes from 192.168.3.1: icmp_seq=1 ttl=64 time=129 ms
1308 bytes from 192.168.3.1: icmp_seq=2 ttl=64 time=129 ms
1308 bytes from 192.168.3.1: icmp_seq=3 ttl=64 time=129 ms
--- server_ip ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2001ms
rtt min/avg/max/mdev = 129.082/129.504/129.809/0.425 ms
Ansia peers # ping -c 3 -s 1400 server_ip
PING server_ip (192.168.3.1) 1400(1428) bytes of data.
--- server_ip ping statistics ---
3 packets transmitted, 0 received, 100% packet loss, time 1999ms
Ansia peers #
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La cosa che mi fa imbestialire e' che utilizzando il client windows (l MTU che concordano il client e ils erver risulta essere sempre 1400 a quando mi pare) tutto va liscio come l'olio.
Leggendo l'help ho provato inoltre ad usare la seguente riga per iptables per effettuare il clamp dell MSS del tcp all mtu del protocollo IP ma senza risultati degni di nota.
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iptables --append FORWARD --protocol tcp --tcp-flags SYN,RST SYN --jump TCPMSS --clamp-mss-to-pmtu
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Qualche idea?
Last edited by Dun on Fri Mar 31, 2006 1:04 am; edited 1 time in total |
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Dun Apprentice
Joined: 17 Apr 2004 Posts: 172 Location: Amsterdam (NL) / Venice (IT)
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Posted: Fri Mar 31, 2006 12:57 am Post subject: |
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Ok questa funziona....
Inserita sul client pero' per permettere al server di spedire pacchetti http.
Inserita sul server per permettere al client di spedire pacchetti http.
Code: |
iptables -A OUTPUT -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --set-mss 1350
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L'opzione "--clamp-mss-to-pmtu" non funziona a quanto sembra...sebbene l MTU risulti settato a 1400 sull'interfaccia ppp0 di tutti e due i pc.
Avete mica una spiegazione logica del comportamento? |
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