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dhcp: Only use DHCP server port if explicitly configured 

If a DHCP server is running on the same host it isn't necessary to
bind the server port and might even cause conflicts.
This commit is contained in:
Tobias Brunner 2018-06-26 15:48:07 +02:00
parent 50c4c1bb40
commit 707b70725a
2 changed files with 22 additions and 2 deletions
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15
conf/plugins/dhcp.opt
View File

@ -15,6 +15,21 @@ charon.plugins.dhcp.identity_lease = no
charon.plugins.dhcp.server = 255.255.255.255
DHCP server unicast or broadcast IP address.
charon.plugins.dhcp.use_server_port = no
Use the DHCP server port (67) as source port when a unicast server address
is configured.
Use the DHCP server port (67) as source port, instead of the DHCP client
port (68), when a unicast server address is configured and the plugin acts
as relay agent. When replying in this mode the DHCP server will always send
packets to the DHCP server port and if no process binds that port an ICMP
port unreachables will be sent back, which might be problematic for some
DHCP servers. To avoid that, enabling this option will cause the plugin to
bind the DHCP server port to send its requests when acting as relay agent.
This is not necessary if a DHCP server is already running on the same host
and might even cause conflicts (and since the server port is already bound,
ICMPs should not be an issue).
charon.plugins.dhcp.interface
Interface name the plugin uses for address allocation.

9
src/libcharon/plugins/dhcp/dhcp_socket.c
View File

@ -800,7 +800,10 @@ dhcp_socket_t *dhcp_socket_create()
destroy(this);
return NULL;
}
if (!is_broadcast(this->dst))
if (!is_broadcast(this->dst) &&
lib->settings->get_bool(lib->settings,
"%s.plugins.dhcp.use_server_port", FALSE,
lib->ns))
{
/* when setting giaddr (which we do when we don't broadcast), the server
* should respond to the server port on that IP, according to RFC 2131,
@ -808,7 +811,9 @@ dhcp_socket_t *dhcp_socket_create()
* kernel will respond with an ICMP port unreachable if there is no
* socket bound to that port, which might be problematic with certain
* DHCP servers. instead of opening an additional socket, that we don't
* actually use, we can also just send our requests from port 67 */
* actually use, we can also just send our requests from port 67.
* we don't do this by default, as it might cause conflicts with DHCP
* servers running on the same host */
src.sin_port = htons(DHCP_SERVER_PORT);
}
if (bind(this->send, (struct sockaddr*)&src, sizeof(src)) == -1)