This commit improves upon the PortMapper and PortAllocator classes by changing
their internal data structures for port allocations to use a string rather than
a single integer. This string holds the network interface address as well as the
port number. This solves a previous problem where a port would be incorrectly
reported as being in use because it had been allocated for a different interface.
I've also added a basic test case for the PortMapper class, and extended the
existing test case for PortAllocator. In the case of PortMapper, this is done
by handing it a stub function for creating proxies rather than an actual
implementation.
Retrieve /etc/resolv.conf data (if available)
Add checkNameserverOverlaps and call it to
make sure there are no conflicts
Add utils.GetNameserversAsCIDR and tests
Read /etc/resolv.conf and pull out nameservers,
formatting them as a CIDR block ("1.2.3.4/32")
API Changes
-----------
The port notation is extended to support "/udp" or "/tcp" at the *end*
of the specifier string (and defaults to tcp if "/tcp" or "/udp" are
missing)
`docker ps` now shows UDP ports as "frontend->backend/udp". Nothing
changes for TCP ports.
`docker inspect` now displays two sub-dictionaries: "Tcp" and "Udp",
under "PortMapping" in "NetworkSettings".
Theses changes stand true for the values returned by the HTTP API too.
This changeset will definitely break tools built upon the API (or upon
`docker inspect`). A less intrusive way to add UDP ports in `docker
inspect` would be to simply add "/udp" for UDP ports but it will still
break existing applications which tries to convert the whole field to an
integer. I believe that having two TCP/UDP sub-dictionaries is better
because it makes the whole thing more clear and more easy to parse right
away (i.e: you don't have to check the format of the string, split it
and convert the right part to an integer)
Code Changes
------------
Significant changes in network.go:
- A second PortAllocator is instantiated for the UDP range;
- PortMapper maintains separate mapping for TCP and UDP;
- The extPorts array in NetworkInterface is now an array of Nat objects
(so we can know on which protocol a given port was mapped when
NetworkInterface.Release() is called);
- TCP proxying on localhost has been moved away in network_proxy.go.
localhost proxy code rewrite in network_proxy.go:
We have to proxy the traffic between localhost:frontend-port and
container:backend-port because Netfilter doesn't work properly on the
loopback interface and DNAT iptable rules aren't applied there.
- Goroutines in the TCP proxying code are now explicitly stopped when
the proxy is stopped;
- UDP connection tracking using a map (more infos in [1]);
- Support for IPv6 (to be more accurate, the code is transparent to the
Go net package, so you can use, tcp/tcp4/tcp6/udp/udp4/udp6);
- Single Proxy interface for both UDP and TCP proxying;
- Full test suite.
[1] https://github.com/dotcloud/docker/issues/33#issuecomment-20010400
Instead of allocating all possible IPs in advance, generate them as
needed.
A loop will cycle through all possible IPs in sequential order,
allocating them as needed and marking them as in use. Once the loop
exhausts all IPs, it will wrap back to the beginning. IPs that are
already in use will be skipped. When an IP is released, it will be
cleared and be available for allocation again.
Two decisions went into this design:
1) Minimize memory footprint by only allocating IPs that are actually
in use
2) Minimize reuse of released IP addresses to avoid sending traffic to
the wrong containers
As a side effect, the functions for IP/Mask<->int conversion have been
rewritten to never be able to fail in order to reduce the amount of
error returns.
Fixes gh-231
