* R: Re: mtu issue with ipsec tunnel and netfilter snat
@ 2013-01-09 9:55 pupilla
0 siblings, 0 replies; 3+ messages in thread
From: pupilla @ 2013-01-09 9:55 UTC (permalink / raw)
To: jengelh; +Cc: netdev
jengelh@inai.de wrote:
>On Wednesday 2013-01-09 10:01, pupilla@libero.it wrote:
>
>>As you can see there are incoming 1500 bytes packets (these are the
>>decrypted ipsec packets) with DF bit set. These packets are never
>>delivered to the final client 10.81.128.176 (the destination address
>>is 172.16.128.1 which is the ip used for SNATing the original ip
>>10.81.128.176).
>>
>>IMHO this is a mtu issue: 1500 bytes packets cannot be routed inside
>>the ipsec tunnel.
>>
>>But why linux_gw_snat is not sending icmp need to frag packets to
>>10.148.12.23?
>
>Perhaps because ICMP was blocked erroneously?
No, I have opened the firewall
rules with something like:
iptables -I OUTPUT --proto icmp -j ACCEPT
iptables -I INPUT --proto icmp -j ACCEPT
^ permalink raw reply [flat|nested] 3+ messages in thread
* R: Re: mtu issue with ipsec tunnel and netfilter snat
@ 2013-01-10 16:46 pupilla
2013-01-10 17:57 ` Jan Engelhardt
0 siblings, 1 reply; 3+ messages in thread
From: pupilla @ 2013-01-10 16:46 UTC (permalink / raw)
To: jengelh; +Cc: netdev
jengelh@inai.de wrote:
>On Wednesday 2013-01-09 10:01, pupilla@libero.it wrote:
>
>>As you can see there are incoming 1500 bytes packets (these are the
>>decrypted ipsec packets) with DF bit set. These packets are never
>>delivered to the final client 10.81.128.176 (the destination address
>>is 172.16.128.1 which is the ip used for SNATing the original ip
>>10.81.128.176).
>>
>>IMHO this is a mtu issue: 1500 bytes packets cannot be routed inside
>>the ipsec tunnel.
>>
>>But why linux_gw_snat is not sending icmp need to frag packets to
>>10.148.12.23?
>
>Perhaps because ICMP was blocked erroneously?
well, I don't see the icmp packets
because tcpdump 'see' only the incoming
ipsec clear packets. Is there a way to
see the outgoing clear ipsec packets
with tcpdump?
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: R: Re: mtu issue with ipsec tunnel and netfilter snat
2013-01-10 16:46 pupilla
@ 2013-01-10 17:57 ` Jan Engelhardt
0 siblings, 0 replies; 3+ messages in thread
From: Jan Engelhardt @ 2013-01-10 17:57 UTC (permalink / raw)
To: pupilla@libero.it; +Cc: netdev
On Thursday 2013-01-10 17:46, pupilla@libero.it wrote:
>jengelh@inai.de wrote:
>>>
>>>But why linux_gw_snat is not sending icmp need to frag packets to
>>>10.148.12.23?
>>
>>Perhaps because ICMP was blocked erroneously?
>
>well, I don't see the icmp packets because tcpdump 'see' only the
>incoming ipsec clear packets. Is there a way to see the outgoing clear
>ipsec packets with tcpdump?
Not with AF_PACKET sockets (tcpdump uses such), but you could with
iptables -j LOG, NFLOG and TRACE they can be made visible. If you need
the full packet, you can either patch up LOG to call the kernel hexdump
functions, or use NFLOG - I think - to deliver it to any userspace
program to do further processing. If all else fails, there is also
NFQUEUE with which the packet can also be copied to userspace.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2013-01-09 9:55 R: Re: mtu issue with ipsec tunnel and netfilter snat pupilla
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2013-01-10 16:46 pupilla
2013-01-10 17:57 ` Jan Engelhardt
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