[strongSwan] Strongswan/VTI: Connection killed after several "retransmit of request"

Gilles Printemps gprintemps at gmail.com
Wed Nov 14 15:51:35 CET 2018


Hi,
Since several months, I'm trying to find a solution for routing traffic
from a specific user to a VPN using VTI.
Issue seems coming from the VTI that I created for handling the VPN
connection (FYI, using the same routing parameters with OpenVPN is
working).

Issue is the following:
   - Connection is successfully established
   - Then following request using VTI/VPN returns successfully a response
     sudo -u vpn -i -- curl ipinfo.io

   - After several attempts to keep the connection alive, connection
breaks, the link with the VPN is broken
     and another run of the previous command returns "curl: (6) Could not
resolve host: ipinfo.io"

I tried to follow advice from users of the mailing list but, unfortunately,
the issue is till there...
Updated config files and logs (ifconfig, iptables, xfrm state, charon.log)
are in attachment.

I'm suspecting that the issue is due to:
   - a missing/bad route
   - an issue related to conn mark
         .. I'm using 0x1 to mark traffic from "vpn" user and to route it
to the VTI
         .. Strongswan is using 0x2 to flag its packets
            BTW, as you can see is the result of "xfrm state", mark 0x2 is
only available in one way.
            All result, I'm seen show the mark in both direction...

I really hope someone will be able to help me for finding a solution...
Thanks in advance
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enp0s5    Link encap:Ethernet  HWaddr 00:1c:42:61:00:5f  
          inet addr:10.211.55.26  Bcast:10.211.55.255  Mask:255.255.255.0
          inet6 addr: fdb2:2c26:f4e4:0:21c:42ff:fe61:5f/64 Scope:Global
          inet6 addr: fe80::21c:42ff:fe61:5f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:30689 errors:0 dropped:0 overruns:0 frame:0
          TX packets:20834 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:3096795 (3.0 MB)  TX bytes:4175200 (4.1 MB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:309 errors:0 dropped:0 overruns:0 frame:0
          TX packets:309 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1 
          RX bytes:29366 (29.3 KB)  TX bytes:29366 (29.3 KB)

tun0      Link encap:IPIP Tunnel  HWaddr   
          inet addr:10.3.190.59  P-t-P:10.3.190.59  Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP  MTU:1480  Metric:1
          RX packets:24 errors:0 dropped:0 overruns:0 frame:0
          TX packets:56 errors:15 dropped:0 overruns:0 carrier:15
          collisions:0 txqueuelen:1 
          RX bytes:4075 (4.0 KB)  TX bytes:3476 (3.4 KB)

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Filter table:Chain INPUT (policy ACCEPT 598 packets, 48232 bytes)
 pkts bytes target     prot opt in     out     source               destination         
   24  4075 ACCEPT     all  --  tun0   any     anywhere             anywhere             ctstate ESTABLISHED
    0     0 REJECT     all  --  tun0   any     anywhere             anywhere             reject-with icmp-port-unreachable

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain OUTPUT (policy ACCEPT 471 packets, 87850 bytes)
 pkts bytes target     prot opt in     out     source               destination         
    0     0 ACCEPT     all  --  any    lo      anywhere             anywhere             owner UID match vpn
    0     0 ACCEPT     all  --  any    tun0    anywhere             anywhere             owner UID match vpn
    0     0 REJECT     all  --  any    enp0s5 !10.211.55.26         anywhere             reject-with icmp-port-unreachable

Nat table:Chain PREROUTING (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain INPUT (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain OUTPUT (policy ACCEPT 26 packets, 1683 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain POSTROUTING (policy ACCEPT 12 packets, 857 bytes)
 pkts bytes target     prot opt in     out     source               destination         
   14   826 MASQUERADE  all  --  any    tun0    anywhere             anywhere            

Mangle table:
Chain PREROUTING (policy ACCEPT 623 packets, 52455 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain INPUT (policy ACCEPT 623 packets, 52455 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
 pkts bytes target     prot opt in     out     source               destination         

Chain OUTPUT (policy ACCEPT 472 packets, 87921 bytes)
 pkts bytes target     prot opt in     out     source               destination         
  472 87921 CONNMARK   all  --  any    any     anywhere             anywhere             CONNMARK restore
  104 11412 MARK       all  --  any    any     anywhere            !10.211.55.26         owner UID match vpn MARK set 0x1
    0     0 MARK       udp  --  any    any     anywhere             10.211.55.26         udp dpt:domain owner UID match vpn MARK set 0x1
    0     0 MARK       tcp  --  any    any     anywhere             10.211.55.26         tcp dpt:domain owner UID match vpn MARK set 0x1
    0     0 MARK       all  --  any    any    !10.211.55.26         anywhere             owner UID match vpn MARK set 0x1
  472 87921 CONNMARK   all  --  any    any     anywhere             anywhere             CONNMARK save

Chain POSTROUTING (policy ACCEPT 528 packets, 91397 bytes)
 pkts bytes target     prot opt in     out     source               destination         
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src 10.211.55.26 dst 109.201.137.51
	proto esp spi 0xcb891ab0 reqid 1 mode tunnel
	replay-window 0 flag af-unspec
	mark 0x2/0xffffffff
	auth-trunc hmac(sha512) 0xb614f7da07f790de4f11e185574d3a36bdaa7c6e6ddb9e9bb04db47b1bc6c482b5878a63336eecc5379f8a66110364bd8aaea79dcb9650aad79be2613bb9a10b 256
	enc cbc(aes) 0x94df611762df1f4306ab2589507de29c10b8b869285786c2cfc8cacc0fd6fa9e
	encap type espinudp sport 4500 dport 4500 addr 0.0.0.0
	anti-replay context: seq 0x0, oseq 0x38, bitmap 0x00000000
src 109.201.137.51 dst 10.211.55.26
	proto esp spi 0xc23a523c reqid 1 mode tunnel
	replay-window 32 flag af-unspec
	auth-trunc hmac(sha512) 0x288d8a1a5deb50ed1a633f3ffab307dcb8adc349554f298cfbd78b1171e16c4ac4d3085e1291de8890db09fb3cd78b2c7cd0277e2d527a207785ee9fd5925ee5 256
	enc cbc(aes) 0x5cf2ceb5b051d7f1510bf70de6ac4d7f53a6b33b15d33df633e7c396f8bc0a12
	encap type espinudp sport 4500 dport 4500 addr 0.0.0.0
	anti-replay context: seq 0x18, oseq 0x0, bitmap 0x00ffffff


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