Added client-bypass-protocol config option

By default, anyconnect clients will drop all traffic of a given IP
version if there is no IP address in that version assigned to the
client. The client-bypass-protocol option, if enabled, will send an
extra header to the clients telling anyconnect client to bypass VPN
tunnel if there is no IP assigned. No impact for openconnect clients,
this header will simply be ignored.

Signed-off-by: Florian Domain <f.domain@criteo.com>

tests/data/test-client-bypass-protocol.config

@@ -0,0 +1,192 @@
+# User authentication method. Could be set multiple times and in that case
+# all should succeed.
+# Options: certificate, pam. 
+auth = "certificate"
+#auth = "plain[@SRCDIR@/data/test-group.passwd]"
+#auth = "pam"
+
+isolate-workers = @ISOLATE_WORKERS@
+
+# A banner to be displayed on clients
+#banner = "Welcome"
+
+# Use listen-host to limit to specific IPs or to the IPs of a provided hostname.
+#listen-host = [IP|HOSTNAME]
+
+use-dbus = no
+
+# Limit the number of clients. Unset or set to zero for unlimited.
+#max-clients = 1024
+max-clients = 16
+
+# Limit the number of client connections to one every X milliseconds 
+# (X is the provided value). Set to zero for no limit.
+#rate-limit-ms = 100
+
+# Limit the number of identical clients (i.e., users connecting multiple times)
+# Unset or set to zero for unlimited.
+max-same-clients = 2
+
+# TCP and UDP port number
+tcp-port = @PORT@
+udp-port = @PORT@
+
+# Keepalive in seconds
+keepalive = 32400
+
+# Dead peer detection in seconds
+dpd = 440
+
+# MTU discovery (DPD must be enabled)
+try-mtu-discovery = false
+
+# The key and the certificates of the server
+# The key may be a file, or any URL supported by GnuTLS (e.g., 
+# tpmkey:uuid=xxxxxxx-xxxx-xxxx-xxxx-xxxxxxxx;storage=user
+# or pkcs11:object=my-vpn-key;object-type=private)
+#
+# There may be multiple certificate and key pairs and each key
+# should correspond to the preceding certificate.
+server-cert = @SRCDIR@/certs/server-cert.pem
+server-key = @SRCDIR@/certs/server-key.pem
+
+# Diffie-Hellman parameters. Only needed if you require support
+# for the DHE ciphersuites (by default this server supports ECDHE).
+# Can be generated using:
+# certtool --generate-dh-params --outfile /path/to/dh.pem
+#dh-params = /path/to/dh.pem
+
+# If you have a certificate from a CA that provides an OCSP
+# service you may provide a fresh OCSP status response within
+# the TLS handshake. That will prevent the client from connecting
+# independently on the OCSP server.
+# You can update this response periodically using:
+# ocsptool --ask --load-cert=your_cert --load-issuer=your_ca --outfile response
+# Make sure that you replace the following file in an atomic way.
+#ocsp-response = /path/to/ocsp.der
+
+# In case PKCS #11 or TPM keys are used the PINs should be available
+# in files. The srk-pin-file is applicable to TPM keys only (It's the storage
+# root key).
+#pin-file = /path/to/pin.txt
+#srk-pin-file = /path/to/srkpin.txt
+
+# The name of the group that if selected it would allow to use
+# the assigned by default group.
+default-select-group = group1
+
+# Instead of specifying manually all the allowed groups, you may instruct
+# ocserv to scan all available groups and include the full list. That
+# option is only functional on plain authentication.
+#auto-select-group = true
+
+select-group = group1
+select-group = group3[Do not tunnel access LAN subnet]
+
+# The Certificate Authority that will be used
+# to verify clients if certificate authentication
+# is set.
+ca-cert = @SRCDIR@/certs/ca.pem
+
+# The object identifier that will be used to read the user ID in the client certificate.
+# The object identifier should be part of the certificate's DN
+# Useful OIDs are: 
+#  CN = 2.5.4.3, UID = 0.9.2342.19200300.100.1.1
+cert-user-oid = 0.9.2342.19200300.100.1.1
+
+# The object identifier that will be used to read the user group in the client 
+# certificate. The object identifier should be part of the certificate's DN
+# Useful OIDs are: 
+#  OU (organizational unit) = 2.5.4.11 
+#cert-group-oid = 2.5.4.11
+
+# A revocation list of ca-cert is set
+#crl = /path/to/crl.pem
+
+# GnuTLS priority string
+tls-priorities = "PERFORMANCE:%SERVER_PRECEDENCE:%COMPAT"
+
+# To enforce perfect forward secrecy (PFS) on the main channel.
+#tls-priorities = "NORMAL:%SERVER_PRECEDENCE:%COMPAT:-RSA"
+
+# The time (in seconds) that a client is allowed to stay connected prior
+# to authentication
+auth-timeout = 40
+
+# The time (in seconds) that a client is not allowed to reconnect after 
+# a failed authentication attempt.
+#min-reauth-time = 2
+
+# Script to call when a client connects and obtains an IP
+# Parameters are passed on the environment.
+# REASON, USERNAME, GROUPNAME, HOSTNAME (the hostname selected by client), 
+# DEVICE, IP_REAL (the real IP of the client), IP_LOCAL (the local IP
+# in the P-t-P connection), IP_REMOTE (the VPN IP of the client). REASON
+# may be "connect" or "disconnect".
+#connect-script = /usr/bin/myscript
+#disconnect-script = /usr/bin/myscript
+
+# UTMP
+use-utmp = true
+
+# PID file
+pid-file = ./ocserv.pid
+
+# The default server directory. Does not require any devices present.
+#chroot-dir = /path/to/chroot
+
+# socket file used for IPC, will be appended with .PID
+# It must be accessible within the chroot environment (if any)
+socket-file = ./ocserv-socket
+
+# The user the worker processes will be run as. It should be
+# unique (no other services run as this user).
+run-as-user = @USERNAME@
+run-as-group = @GROUP@
+
+# Network settings
+
+device = vpns
+
+# The default domain to be advertised
+default-domain = example.com
+
+ipv4-network = 192.168.1.0
+ipv4-netmask = 255.255.255.0
+# Use the keywork local to advertize the local P-t-P address as DNS server
+ipv4-dns = 192.168.1.1
+
+# The NBNS server (if any)
+#ipv4-nbns = 192.168.2.3
+
+#ipv6-address = 
+#ipv6-mask = 
+#ipv6-dns = 
+
+# Prior to leasing any IP from the pool ping it to verify that
+# it is not in use by another (unrelated to this server) host.
+ping-leases = false
+
+# Leave empty to assign the default MTU of the device
+# mtu = 
+
+no-route = 192.168.98.0/255.255.255.0
+route = default
+
+#
+# The following options are for (experimental) AnyConnect client 
+# compatibility. They are only available if the server is built 
+# with --enable-anyconnect
+#
+
+# Client profile xml. A sample file exists in doc/profile.xml.
+# This file must be accessible from inside the worker's chroot. 
+# The profile is ignored by the openconnect client.
+#user-profile = profile.xml
+
+# Unless set to false it is required for clients to present their
+# certificate even if they are authenticating via a previously granted
+# cookie. Legacy CISCO clients do not do that, and thus this option
+# should be set for them.
+#always-require-cert = false
+