docs: markdown documentation section (sidebar nav, per-page toc, search, hljs)

content/docs/linking.md

@@ -0,0 +1,45 @@
+# Server links
+
+echoIRCd links to other servers — and to echo services — over a standard server-to-server
+protocol, wire-compatible with the InspIRCd 1206 protocol.
+
+## Server identity
+
+Every server needs a unique **SID** (three characters, the first a digit) and a name.
+
+```ini
+network "echoiRCd";
+sid     "0AA";
+```
+
+## A link block
+
+Each `link` block describes a peer: its name, address, port, and the passwords used to
+authenticate the connection in each direction.
+
+```ini
+listen { ip "[::]"; port 7700; type server; }
+
+link {
+    name         "hub.example.net";
+    ip           "203.0.113.10";
+    port         7700;
+    sendpassword "outbound-secret";
+    recvpassword "inbound-secret";
+}
+```
+
+> Treat link passwords as secrets, and restrict the server port to trusted peers.
+
+## Services
+
+echo services connect as a special linked server. In the ircd, mark the services server name as a
+**U-lined** server (and as the SASL server) so its privileged commands and SASL relay are
+accepted:
+
+```ini
+uline { server "services.echoircd.org"; }
+sasl_server "services.echoircd.org";
+```
+
+See [Services](/docs/services) for the services side of the link.