path: root/conf
diff options
authorMartin Willi <martin@strongswan.org>2016-09-16 14:50:07 +0200
committerTobias Brunner <tobias@strongswan.org>2017-05-23 16:49:39 +0200
commit9b29003cd9e12075070106eb9481954ab34912ca (patch)
treedde24a01c6a66630aa1ad5964558f77e97b65691 /conf
parent46a3f92a76b748a3086912215e14a3c9f1a5a98b (diff)
socket-default: Add an option to force the sending interface via IP_PKTINFO
On Linux, setting the source address is insufficient to force a packet to be sent over a certain path. The kernel uses the best route to select the outgoing interface, even if we set a source address of a lower priority interface. This is not only true for interfaces attaching to the same subnet, but also for unrelated interfaces; the kernel (at least on 4.7) sends out the packet on whatever interface it sees fit, even if that network does not expect packets from the source address we force to. When a better interface becomes available, strongSwan sends its MOBIKE address list update using the old source address. But the kernel sends that packet over the new best interface. If that network drops packets having the unexpected source address from the old path, the MOBIKE update fails and the SA finally times out. To enforce a specific interface for our packet, we explicitly set the interface index from the interface where the source address is installed. According to ip(7), this overrules the specified source address to the primary interface address. As this could have side effects to installations using multiple addresses on a single interface, we disable the option by default for now. This also allows using IPv6 link-local addresses, which won't work if the outbound interface is not set explicitly.
Diffstat (limited to 'conf')
1 files changed, 6 insertions, 0 deletions
diff --git a/conf/plugins/socket-default.opt b/conf/plugins/socket-default.opt
index 483a0f03d..570bd0ec7 100644
--- a/conf/plugins/socket-default.opt
+++ b/conf/plugins/socket-default.opt
@@ -4,6 +4,12 @@ charon.plugins.socket-default.fwmark =
charon.plugins.socket-default.set_source = yes
Set source address on outbound packets, if possible.
+charon.plugins.socket-default.set_sourceif = no
+ Force sending interface on outbound packets, if possible.
+ Force sending interface on outbound packets, if possible. This allows
+ using IPv6 link-local addresses as tunnel endpoints.
charon.plugins.socket-default.use_ipv4 = yes
Listen on IPv4, if possible.