We use SIGALRM to limit runtime of dpctl and ofp-discover. There is no
reason that we should not clean up after it in the same way as any other
catchable signal. In particular, ofp-discover wants to restore network
device flags on timeout.
The upcoming ofp-discover program wants to print out the binding
information, and dhcp_msg_to_string() is pretty close to what it
wants. But one-field-per-line is easier for other programs to parse.
This allows us to have DHCP clients that don't actually bind or unbind
a network device's IP address. This is useful for doing controller
discovery without actually reconfiguring a network device.
There's no need to set changed unconditionally in dhclient_init(), and
it can make extra work for the users of the dhclient, by causing them
to think that something changed when it didn't.
libtool was needed when NOX was directly linking against libopenflow.
Since it doesn't do that anymore, we can drop its use (and that makes
OpenFlow configure and build slightly faster).
We can't guarantee uniqueness of ip_id versus the host's, screwing up
fragment reassembly, so prevent fragmentation and use an all-zeros
ip_id. RFC 791 doesn't say we can do this, but Linux does the same
thing for DF packets, so it must not screw anything up.
The secure channel, in discovery mode, wants to enable TCP connections
by default only if SSL has not been configured. This function allows
it to do that.
Otherwise, the TCP/IP implementation is responsible for connection
attempt backoff, but we want to have some control over it ourselves.
In particular we want to initially back off faster and to log a
message upon connection attempt retransmission, to make it easier
to see what has happened from the log.
Similarly for buffer_reserve_tailroom.
The new name better reflects what they do, and make way for a different
use of the term "reserve" in the upcoming buffer_reserve() function.
It seems that this should be useful for debugging post-mortems. Also,
this ensures that the "current time is negative" log message appears in
syslog. Otherwise, it won't ever, because we log it before the vlog
client has a chance to configure its log levels.
Previously we set a few timers to expire at a time_t of 0, i.e.
immediately. But if the system date is set incorrectly to a date
before 1970, then these timers will essentially never expire.
Set them to expire at TIME_MIN instead.
The secchan needs to handle ARP requests from the controller itself, so
it has to translate the controller's IP address into a MAC address to
allow it to match those packets on dl_src. (OpenFlow doesn't allow us
to look into ARP packets and match on the encapsulated IP addresses, so
this is the best we can do.)
Ben Pfaff