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Joseph Henry
2016-06-27 12:27:51 -07:00
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docs/linux_zt_sdk.md
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@@ -13,24 +13,26 @@ See [doc/docker_linux_zt_sdk.md](doc/docker_linux_zt_sdk.md)
## Dynamic Linking
To build the service host, IP stack, and intercept library, from the base of the ZeroTier One tree run:
**Step 1: Build the libraries and intercept:**
make shared_lib
`make linux_shared_lib`
This will build a binary called `zerotier-sdk-service` and a library called `libztintercept.so`. It will also build the IP stack as `build/liblwip.so`.
The `zerotier-sdk-service` binary is almost the same as a regular ZeroTier One build except instead of creating virtual network ports using Linux's `/dev/net/tun` interface, it creates instances of a user-space TCP/IP stack for each virtual network and provides RPC access to this stack via a Unix domain socket. The latter is a library that can be loaded with the Linux `LD_PRELOAD` environment variable or by placement into `/etc/ld.so.preload` on a Linux system or container. Additional magic involving nameless Unix domain socket pairs and interprocess socket handoff is used to emulate TCP sockets with extremely low overhead and in a way that's compatible with select, poll, epoll, and other I/O event mechanisms.
*The `zerotier-sdk-service` binary is almost the same as a regular ZeroTier One build except instead of creating virtual network ports using Linux's `/dev/net/tun` interface, it creates instances of a user-space TCP/IP stack for each virtual network and provides RPC access to this stack via a Unix domain socket. The latter is a library that can be loaded with the Linux `LD_PRELOAD` environment variable or by placement into `/etc/ld.so.preload` on a Linux system or container. Additional magic involving nameless Unix domain socket pairs and interprocess socket handoff is used to emulate TCP sockets with extremely low overhead and in a way that's compatible with select, poll, epoll, and other I/O event mechanisms.*
The intercept library does nothing unless the `ZT_NC_NETWORK` environment variable is set. If on program launch (or fork) it detects the presence of this environment variable, it will attempt to connect to a running `zerotier-sdk-service` at the specified Unix domain socket path.
*The intercept library does nothing unless the `ZT_NC_NETWORK` environment variable is set. If on program launch (or fork) it detects the presence of this environment variable, it will attempt to connect to a running `zerotier-sdk-service` at the specified Unix domain socket path.*
Unlike `zerotier-one`, `zerotier-sdk-service` does not need to be run with root privileges and will not modify the host's network configuration in any way. It can be run alongside `zerotier-one` on the same host with no ill effect, though this can be confusing since you'll have to remember the difference between "real" host interfaces (tun/tap) and network containerized endpoints. The latter are completely unknown to the kernel and will not show up in `ifconfig`.
*Unlike `zerotier-one`, `zerotier-sdk-service` does not need to be run with root privileges and will not modify the host's network configuration in any way. It can be run alongside `zerotier-one` on the same host with no ill effect, though this can be confusing since you'll have to remember the difference between "real" host interfaces (tun/tap) and network containerized endpoints. The latter are completely unknown to the kernel and will not show up in `ifconfig`.*
**Step 2: **
#### Starting the SDK Service
A simple test can be performed in user space (no root) in your own home directory.
First, build the SDK service and intercept library as described above. Then create a directory to act as a temporary ZeroTier home for your test SDK service instance. You'll need to move the `liblwip.so` binary that was built with `make shared_lib` into there, since the service must be able to find it there and load it.
First, build the SDK service and intercept library as described above. Then create a directory to act as a temporary ZeroTier home for your test SDK service instance. You'll need to move the `liblwip.so` binary that was built with `make linux_shared_lib` into there, since the service must be able to find it there and load it.
mkdir /tmp/sdk-test-home
cp -f build/liblwip.so /tmp/sdk-test-home