Strongswan works on embedded device via ethernet but not with 4G modem
I have a Gateworks SBC with an installed Ubuntu 20.04. My SOC is connected with an USB to ethernet adapter (eth0) as DHCP Client (192.168.88.102) to my Mikrotik router (DHCP Server), which acts as my gateway to internet(Masquerade).
I have installed a virtual Mikrotik instance on AWS, Ip address 18.x.x.x. There I configured an Ipsec Ikev2 tunnel with certificates. Roadwarrior clients should connect with virtual IPs 192.168.11.0/24 (Template). My configuration is identical to Mikrotik Ipsec Wiki.
Via Strongswan I connect my SBC to my Mikrotik AWS router. My SOC acts as a roadwarrior client(Virtual IP 192.168.11.254). Connection is established, SAs are assigned. I can ping from my SOC to 8.8.8.8, and packets are tunneled via my Mikrotik IPSEC router and send back. Everything great till now.
Hint: I disconnect USB to ethernet Adapter now to avoid any problems.
My Gateworks SBC has an installed Toby L210 4G USB Modem. Ubuntu has recognized the modem. I configured the modem to work in Router Mode as described by u-blox. With Modemmanager I send a command to connect to my Telekom Provider. Than I send command "dhclient wwan0" to create wwan0 interface and get the IP Address 192.168.1.100 from DHCP Server of modem. 192.168.1.1 is gateway address of modem. Ping to google works. My Modem has an internal IP address of 100.64.x.x (Carrier grade NAT)
Now I start Strongswan (ipsec up test). Again connection is established, SAs are distributed. But I cannot ping 8.8.8.8 It is interesting that if I ping to 8.8.8.8 I see the incoming packets at my Mikrotik IPSEC server(packet sniffer), which is forwarding to 8.8.8.8 and sending the answer back to the tunnel. So the outgoing packets from my SBC work I guess...
Ping Dump with 4G Modem, Ping is not answered
1 0.000000000 192.168.1.100 18.xxx.xxx.xxx ESP 174 ESP (SPI=0x0b2a5a40)
2 0.063911734 18.xxx.xxx.xxx 192.168.1.100 ESP 174 ESP (SPI=0xcbb1d2c0)
3 0.486664666 18.xxx.xxx.xxx 192.168.1.100 ISAKMP 202 INFORMATIONAL MID=65 Responder Request
4 0.488833047 192.168.1.100 18.xxx.xxx.xxx ISAKMP 122 INFORMATIONAL MID=65 Initiator Response
5 1.019959021 192.168.1.100 18.xxx.xxx.xxx ESP 174 ESP (SPI=0x0b2a5a40)
6 1.088668527 18.xxx.xxx.xxx 192.168.1.100 ESP 174 ESP (SPI=0xcbb1d2c0)
7 2.043874128 192.168.1.100 18.xxx.xxx.xxx ESP 174 ESP (SPI=0x0b2a5a40)
8 2.133560094 18.xxx.xxx.xxx 192.168.1.100 ESP 174 ESP (SPI=0xcbb1d2c0)
9 3.067978240 192.168.1.100 18.xxx.xxx.xxx ESP 174 ESP (SPI=0x0b2a5a40)
10 3.163589336 18.xxx.xxx.xxx 192.168.1.100 ESP 174 ESP (SPI=0xcbb1d2c0)
11 4.091881681 192.168.1.100 18.xxx.xxx.xxx ESP 174 ESP (SPI=0x0b2a5a40)
12 4.168360691 18.xxx.xxx.xxx 192.168.1.100 ESP 174 ESP (SPI=0xcbb1d2c0)
13 5.115993793 192.168.1.100 18.xxx.xxx.xxx ESP 174 ESP (SPI=0x0b2a5a40)
14 5.193667829 18.xxx.xxx.xxx 192.168.1.100 ESP 174 ESP (SPI=0xcbb1d2c0)
15 5.566650670 18.xxx.xxx.xxx 192.168.1.100 ISAKMP 186 INFORMATIONAL MID=66 Responder Request
16 5.568814384 192.168.1.100 18.xxx.xxx.xxx ISAKMP 122 INFORMATIONAL MID=66 Initiator Response
Ping Dump with eth0, Ping is answered
2 0.227289053 192.168.88.102 18.xxx.xxx.xxx ESP 174 ESP (SPI=0x05bce76a)
3 0.245391122 18.xxx.xxx.xxx 192.168.88.102 ESP 174 ESP (SPI=0xc7c756b9)
4 0.245391122 8.8.8.8 192.168.11.254 ICMP 98 Echo (ping) reply id=0x0002, seq=9/2304, ttl=111
9 1.229264659 192.168.88.102 18.xxx.xxx.xxx ESP 174 ESP (SPI=0x05bce76a)
10 1.243413640 18.xxx.xxx.xxx 192.168.88.102 ESP 174 ESP (SPI=0xc7c756b9)
11 1.243413640 8.8.8.8 192.168.11.254 ICMP 98 Echo (ping) reply id=0x0002, seq=10/2560, ttl=111
12 1.651801718 18.xxx.xxx.xxx 192.168.88.102 ISAKMP 186 INFORMATIONAL MID=04 Responder Request
13 1.654115436 192.168.88.102 18.xxx.xxx.xxx ISAKMP 122 INFORMATIONAL MID=04 Initiator Response
Ipsec.conf
# ipsec.conf - strongSwan IPsec configuration file
# basic configuration
config setup
# strictcrlpolicy=yes
# uniqueids = no
# Add connections here.
# Sample VPN connections
#conn sample-self-signed
# leftsubnet=10.1.0.0/16
# leftcert=selfCert.der
# leftsendcert=never
# right=192.168.0.2
# rightsubnet=10.2.0.0/16
# rightcert=peerCert.der
# auto=start
#conn sample-with-ca-cert
# leftsubnet=10.1.0.0/16
# leftcert=myCert.pem
# right=192.168.0.2
# rightsubnet=10.2.0.0/16
# rightid="C=CH, O=Linux strongSwan CN=peer name"
# auto=start
conn test
keyexchange=ikev2
ike=aes128-sha1-modp2048
esp=aes128-sha1-modp2048
ikelifetime = 24h
lifetime = 30m
dpddelay = 120s
left=%defaultroute
leftsourceip=%modeconfig
leftcert=cert_export_Ventana.pem
leftid=VentanaTest
leftfirewall=yes
right=18.xxx.xxx.xxx
rightsubnet=0.0.0.0/0
rightid="18.xxx.xxx.xxx"
auto=add
ipsec statusall
Status of IKE charon daemon (strongSwan 5.8.2, Linux 5.4.45-g334256aa8a89, armv7l):
uptime: 6 minutes, since Dec 12 20:06:32 2020
malloc: sbrk 1347584, mmap 0, used 457608, free 889976
worker threads: 11 of 16 idle, 5/0/0/0 working, job queue: 0/0/0/0, scheduled: 3
loaded plugins: charon aes rc2 sha2 sha1 md5 mgf1 random nonce x509 revocation constraints pubkey pkcs1 pkcs7 pkcs8 pkcs12 pgp dnskey sshkey pem openssl fips-prf gmp agent xcbc hmac gcm drbg attr kernel-netlink resolve socket-default connmark farp stroke updown eap-identity eap-aka eap-md5 eap-gtc eap-mschapv2 eap-dynamic eap-radius eap-tls eap-ttls eap-peap eap-tnc xauth-generic xauth-eap xauth-pam tnc-tnccs dhcp lookip error-notify certexpire led addrblock unity counters
Listening IP addresses:
192.168.1.100
Connections:
test: %any...18.xxx.xxx.xxx IKEv2
test: local: [CN=VentanaTest] uses public key authentication
test: cert: "CN=VentanaTest"
test: remote: [18.xxx.xxx.xxx] uses public key authentication
test: child: dynamic === 0.0.0.0/0 TUNNEL
Security Associations (1 up, 0 connecting):
test[1]: ESTABLISHED 65 seconds ago, 192.168.1.100[CN=VentanaTest]...18.xxx.xxx.xxx[18.xxx.xxx.xxx]
test[1]: IKEv2 SPIs: 0f0ebcd1d3f24257_i* 0bdabee4cebd469b_r, public key reauthentication in 23 hours
test[1]: IKE proposal: AES_CBC_128/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_2048
test{1}: INSTALLED, TUNNEL, reqid 1, ESP in UDP SPIs: c91f7359_i 005ce3a7_o
test{1}: AES_CBC_128/HMAC_SHA1_96, 0 bytes_i, 5068 bytes_o, (66pkts, 58s ago), rekeying in 14 minutes
test{1}: 192.168.11.254/32 === 0.0.0.0/0
ip xfrm policy
src 192.168.11.254/32 dst 0.0.0.0/0
dir out priority 383615
tmpl src 192.168.1.100 dst 18.xxx.xxx.xxx
proto esp spi 0x005ce3a7 reqid 1 mode tunnel
src 0.0.0.0/0 dst 192.168.11.254/32
dir fwd priority 383615
tmpl src 18.xxx.xxx.xxx dst 192.168.1.100
proto esp reqid 1 mode tunnel
src 0.0.0.0/0 dst 192.168.11.254/32
dir in priority 383615
tmpl src 18.xxx.xxx.xxx dst 192.168.1.100
proto esp reqid 1 mode tunnel
src 0.0.0.0/0 dst 0.0.0.0/0
socket in priority 0
src 0.0.0.0/0 dst 0.0.0.0/0
socket out priority 0
src 0.0.0.0/0 dst 0.0.0.0/0
socket in priority 0
src 0.0.0.0/0 dst 0.0.0.0/0
socket out priority 0
src ::/0 dst ::/0
socket in priority 0
src ::/0 dst ::/0
socket out priority 0
src ::/0 dst ::/0
socket in priority 0
src ::/0 dst ::/0
socket out priority 0
iptables-save
# Generated by iptables-save v1.8.4 on Sat Dec 12 20:24:03 2020
*filter
:INPUT ACCEPT [235:34857]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [224:27000]
-A INPUT -d 192.168.11.254/32 -i wwan0 -m policy --dir in --pol ipsec --reqid 1 --proto esp -j ACCEPT
-A FORWARD -d 192.168.11.254/32 -i wwan0 -m policy --dir in --pol ipsec --reqid 1 --proto esp -j ACCEPT
-A FORWARD -s 192.168.11.254/32 -o wwan0 -m policy --dir out --pol ipsec --reqid 1 --proto esp -j ACCEPT
-A OUTPUT -s 192.168.11.254/32 -o wwan0 -m policy --dir out --pol ipsec --reqid 1 --proto esp -j ACCEPT
COMMIT
ip route show table all
default via 192.168.1.1 dev wwan0 table 220 proto static src 192.168.11.254
default via 192.168.1.1 dev wwan0
192.168.1.0/24 dev wwan0 proto kernel scope link src 192.168.1.100
broadcast 127.0.0.0 dev lo table local proto kernel scope link src 127.0.0.1
local 127.0.0.0/8 dev lo table local proto kernel scope host src 127.0.0.1
local 127.0.0.1 dev lo table local proto kernel scope host src 127.0.0.1
broadcast 127.255.255.255 dev lo table local proto kernel scope link src 127.0.0.1
broadcast 192.168.1.0 dev wwan0 table local proto kernel scope link src 192.168.1.100
local 192.168.1.100 dev wwan0 table local proto kernel scope host src 192.168.1.100
broadcast 192.168.1.255 dev wwan0 table local proto kernel scope link src 192.168.1.100
local 192.168.11.254 dev wwan0 table local proto kernel scope host src 192.168.11.254
::1 dev lo proto kernel metric 256 pref medium
fe80::/64 dev wwan0 proto kernel metric 256 pref medium
local ::1 dev lo table local proto kernel metric 0 pref medium
local fe80::8c85:a8ff:fe59:1d79 dev wwan0 table local proto kernel metric 0 pref medium
ff00::/8 dev wwan0 table local metric 256 pref medium
ip address
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: wwan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 8e:85:a8:59:1d:79 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.100/24 brd 192.168.1.255 scope global dynamic wwan0
valid_lft 42250sec preferred_lft 42250sec
inet 192.168.11.254/32 scope global wwan0
valid_lft forever preferred_lft forever
inet6 fe80::8c85:a8ff:fe59:1d79/64 scope link
valid_lft forever preferred_lft forever
ip -s xfrm state after same pings to 8.8.8.8
root@focal-ventana:~# ip -s xfrm state
src 192.168.1.100 dst 18.xxx.xxx.xxx
proto esp spi 0x0ce2b2ec(216183532) reqid 1(0x00000001) mode tunnel
replay-window 0 seq 0x00000000 flag af-unspec (0x00100000)
auth-trunc hmac(sha1) 0x960b069b0a13ba25dcb30b85f8d5c7ce62efce48 (160 bits) 96
enc cbc(aes) 0x032cc1a7afb2035dd4b6124bf0a845f7 (128 bits)
encap type espinudp sport 4500 dport 4500 addr 0.0.0.0
anti-replay context: seq 0x0, oseq 0xd, bitmap 0x00000000
lifetime config:
limit: soft (INF)(bytes), hard (INF)(bytes)
limit: soft (INF)(packets), hard (INF)(packets)
expire add: soft 2921(sec), hard 3600(sec)
expire use: soft 0(sec), hard 0(sec)
lifetime current:
1092(bytes), 13(packets)
add 2020-12-14 20:26:13 use 2020-12-14 20:36:15
stats:
replay-window 0 replay 0 failed 0
src 18.xxx.xx.x dst 192.168.1.100
proto esp spi 0xc56be3e6(3312182246) reqid 1(0x00000001) mode tunnel
replay-window 32 seq 0x00000000 flag af-unspec (0x00100000)
auth-trunc hmac(sha1) 0xa6789f18e159b6abc44c20850bada3b903c9a161 (160 bits) 96
enc cbc(aes) 0xf6b72416ee9c739502a67dc14883334b (128 bits)
encap type espinudp sport 4500 dport 4500 addr 0.0.0.0
anti-replay context: seq 0x0, oseq 0x0, bitmap 0x00000000
lifetime config:
limit: soft (INF)(bytes), hard (INF)(bytes)
limit: soft (INF)(packets), hard (INF)(packets)
expire add: soft 2582(sec), hard 3600(sec)
expire use: soft 0(sec), hard 0(sec)
lifetime current:
0(bytes), 0(packets)
add 2020-12-14 20:26:13 use -
stats:
replay-window 0 replay 0 failed 0
/proc/net/xfrm_stat
root@focal-ventana:~# vi /proc/net/xfrm_stat
XfrmInError 0
XfrmInBufferError 0
XfrmInHdrError 0
XfrmInNoStates 0
XfrmInStateProtoError 0
XfrmInError 0
XfrmInBufferError 0
XfrmInHdrError 0
XfrmInNoStates 0
XfrmInStateProtoError 0
XfrmInStateModeError 0
XfrmInStateSeqError 0
XfrmInStateExpired 0
XfrmInStateMismatch 0
XfrmInStateInvalid 0
XfrmInTmplMismatch 0
XfrmInNoPols 0
XfrmInPolBlock 0
XfrmInPolError 0
XfrmOutError 0
XfrmOutBundleGenError 0
XfrmOutBundleCheckError 0
XfrmOutNoStates 0
XfrmOutStateProtoError 0
XfrmOutStateModeError 0
XfrmOutStateSeqError 0
XfrmOutStateExpired 0
XfrmOutPolBlock 0
XfrmOutPolDead 0
XfrmOutPolError 0
XfrmFwdHdrError 0
XfrmOutStateInvalid 0
XfrmAcquireError 0
iptables -t nat -L
Chain PREROUTING (policy ACCEPT)
target prot opt source destination
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
1 Answer
So, its working.
The Toby L210 4G modem uses as a factory default RNDIS as a virtual Ethernet link. RNDIS caused problems with my network traffic, even without IPSEC, so I switched to CDC-ECM.
From ublox AT Commands manual:
On a Linux system, to reach the maximum throughput it is necessary to recompile the kernel. Apply the following modification in /kernel/drivers/net/usb/usbnet.c:
Replace "size_t size = dev->rx_urb_size;"with "size_t size = (16*1024);
"If it is not possible to recompile the kernel, then try to use CDC-ECM.
Now CDC-ECM caused my IPSEC to lose my incoming traffic somewhere so I switched back to RNDIS with driver optimization deactivated.
The RNDIS interface may not work if Linux kernel version of the DTE is higher than 4.8 and RNDIS driver optimization is enabled (AT+UDCONF=67,1).
The reported behavior is due to the “rndis_host:
Set valid random MAC on buggy devices” patch introduced in the Kernel version v4.8-rc1:
https://github.com/torvalds/linux/commit/a5a18bdf7453d505783e40e47ebb84bfdd35f93b#diff6dfe16ca0bdcdc21501ef11cfd202a10
The patch presents an incompatibility with the RNDIS driver optimization, which leads to a TCP and UDP traffic lost.
The issue is not present if the RNDIS driver optimization is disabled (AT+UDCONF=67,0), however this may lead to lower throughput.
answered on Server Fault Dec 15, 2020 by 
Gerbaum
GerbaumUser contributions licensed under CC BY-SA 3.0