Support SPIFFE mTLS between Traefik and Backend servers

docs/content/routing/services/index.md

@@ -776,6 +776,82 @@ spec:
     peerCertURI: foobar
 ```
 
+#### `spiffe`
+
+Please note that [SPIFFE](../../https/spiffe.md) must be enabled in the static configuration
+before using it to secure the connection between Traefik and the backends.
+
+##### `spiffe.ids`
+
+_Optional_
+
+`ids` defines the allowed SPIFFE IDs. 
+This takes precedence over the SPIFFE TrustDomain.
+
+```yaml tab="File (YAML)"
+## Dynamic configuration
+http:
+  serversTransports:
+    mytransport:
+      spiffe:
+        ids:
+          - spiffe://trust-domain/id1
+          - spiffe://trust-domain/id2
+```
+
+```toml tab="File (TOML)"
+## Dynamic configuration
+[http.serversTransports.mytransport.spiffe]
+  ids = ["spiffe://trust-domain/id1", "spiffe://trust-domain/id2"]
+```
+
+```yaml tab="Kubernetes"
+apiVersion: traefik.containo.us/v1alpha1
+kind: ServersTransport
+metadata:
+  name: mytransport
+  namespace: default
+
+spec:
+    spiffe:
+      ids:
+        - spiffe://trust-domain/id1
+        - spiffe://trust-domain/id2
+```
+
+##### `spiffe.trustDomain`
+
+_Optional_
+
+`trustDomain` defines the allowed SPIFFE trust domain.
+
+```yaml tab="File (YAML)"
+## Dynamic configuration
+http:
+  serversTransports:
+    mytransport:
+        spiffe:
+          trustDomain: spiffe://trust-domain
+```
+
+```toml tab="File (TOML)"
+## Dynamic configuration
+[http.serversTransports.mytransport.spiffe]
+  trustDomain = "spiffe://trust-domain"
+```
+
+```yaml tab="Kubernetes"
+apiVersion: traefik.containo.us/v1alpha1
+kind: ServersTransport
+metadata:
+  name: mytransport
+  namespace: default
+
+spec:
+    spiffe:
+      trustDomain: "spiffe://trust-domain"
+```
+
 #### `forwardingTimeouts`
 
 `forwardingTimeouts` are the timeouts applied when forwarding requests to the servers.