+ Add default seccomp profile [#18780](https://github.com/docker/docker/pull/18780)
+ Add `--authorization-plugin` flag to `daemon` to customize ACLs [#15365](https://github.com/docker/docker/pull/15365)
+ Docker Content Trust now supports the ability to read and write user delegations [#18887](https://github.com/docker/docker/pull/18887)
This is an optional, opt-in feature that requires the explicit use of the Notary command-line utility in order to be enabled.
Enabling delegation support in a specific repository will break the ability of Docker 1.9 and 1.8 to pull from that repository, if content trust is enabled.
* Allow SELinux to run in a container when using the BTRFS storage driver [#16452](https://github.com/docker/docker/pull/16452)
### Distribution
* Use content-addressable storage for images and layers [#17924](https://github.com/docker/docker/pull/17924)
A migration is performed the first time docker is run; it can take a significant amount of time depending on the number of images and containers present.
Images no longer depend on the parent chain but contain a list of layer references.
`docker load`/`docker save` tarballs now also contain content-addressable image configurations.
For more information: https://github.com/docker/docker/wiki/Engine-v1.10.0-content-addressability-migration
* Add support for the new [manifest format ("schema2")](https://github.com/docker/distribution/blob/master/docs/spec/manifest-v2-2.md) [#18785](https://github.com/docker/docker/pull/18785)
* Lots of improvements for push and pull: performance++, retries on failed downloads, cancelling on client disconnect [#18353](https://github.com/docker/docker/pull/18353), [#18418](https://github.com/docker/docker/pull/18418), [#19109](https://github.com/docker/docker/pull/19109), [#18353](https://github.com/docker/docker/pull/18353)
* Limit v1 protocol fallbacks [#18590](https://github.com/docker/docker/pull/18590)
- Fix issue where docker could hang indefinitely waiting for a nonexistent process to pull an image [#19743](https://github.com/docker/docker/pull/19743)
### Networking
+ Use DNS-based discovery instead of `/etc/hosts` [#19198](https://github.com/docker/docker/pull/19198)
+ Support for network-scoped alias using `--net-alias` on `run` and `--alias` on `network connect` [#19242](https://github.com/docker/docker/pull/19242)
+ Add `--ip` and `--ip6` on `run` and `network connect` to support custom IP addresses for a container in a network [#19001](https://github.com/docker/docker/pull/19001)
+ Add `--ipam-opt` to `network create` for passing custom IPAM options [#17316](https://github.com/docker/docker/pull/17316)
+ Add `--internal` flag to `network create` to restrict external access to and from the network [#19276](https://github.com/docker/docker/pull/19276)
+ Add `kv.path` option to `--cluster-store-opt` [#19167](https://github.com/docker/docker/pull/19167)
+ Add `discovery.heartbeat` and `discovery.ttl` options to `--cluster-store-opt` to configure discovery TTL and heartbeat timer [#18204](https://github.com/docker/docker/pull/18204)
+ Add `--format` flag to `network inspect` [#17481](https://github.com/docker/docker/pull/17481)
+ Add `--link` to `network connect` to provide a container-local alias [#19229](https://github.com/docker/docker/pull/19229)
+ Support for Capability exchange with remote IPAM plugins [#18775](https://github.com/docker/docker/pull/18775)
+ Add `--force` to `network disconnect` to force container to be disconnected from network [#19317](https://github.com/docker/docker/pull/19317)
* Support for multi-host networking using built-in overlay driver for all engine supported kernels: 3.10+ [#18775](https://github.com/docker/docker/pull/18775)
* `--link` is now supported on `docker run` for containers in user-defined network [#19229](https://github.com/docker/docker/pull/19229)
* Enhance `docker network rm` to allow removing multiple networks [#17489](https://github.com/docker/docker/pull/17489)
* Include container names in `network inspect` [#17615](https://github.com/docker/docker/pull/17615)