Skydive is an open source real-time network topology and protocols analyzer. It aims to provide a comprehensive way of understanding what is happening in the network infrastructure.
Skydive agents collect topology informations and flows and forward them to a central agent for further analysis. All the informations are stored in an Elasticsearch database.
Skydive is SDN-agnostic but provides SDN drivers in order to enhance the topology and flows informations.
Topology probes are used to construct the graph comprising:
- Graph nodes: depicted as cycles (in contracted form) or areas (in expanded form)
- Graph edges: depicted as strait lines (with arrowheads when directional)
Agent Topology Probes
Probes which extract topological information from the host about host residing entities are agent probes:
- Docker (docker)
- Ethtool (ethtool)
- LibVirt (libvirt)
- LLDP (lldp)
- Lxd (lxd)
- NetLINK (netlink)
- NetNS (netns)
- Neutron (neutron)
- OVSDB (ovsdb)
- Opencontrail (opencontrail)
- runC (runc)
- Socket Information (socketinfo)
- VPP (vpp)
Analyzer Topology Probes
Probes which extract topological information from a remote global entity are analyzer probes:
- Istio (istio)
- Kubernetes (k8s)
- OVN (ovn)
The k8s probe provides topological information.
- general: cluster, namespace
- compute: node, pod, container
- storage: persistentvolumeclaim (pvc), persistentvolume (pv), storageclass
- network: networkpolicy, service, endpoints, ingress
- deployment: deployment, statefulset, replicaset, replicationcontroller, cronjob, job
- configuration: configmap, secret
- k8s-k8s ownership (e.g. k8s.namespace – k8s.pod)
- k8s-k8s relationship (e.g. k8s.service – k8s.pod)
- k8s-physical relationship (e.g. k8s.node – host)
Graph node metadata:
- indexed fields: standard fields such as
Nameplus k8s specific such as
- stored-only fields: the entire content of k8s resource stored under
Graph node status:
Statusnode metadata field
- with values Up (white) / Down (red)
- currently implemented for resources: pod, persistentvolumeclaim (pvc) and persistentvolume (pv)
Flow Probes supported
Flow probes currently implemented :
- PCAP socket
- OpenvSwitch port mirroring
Skydive relies on a event based graph engine, which means that notifications
are sent for each modification. Graphs expose notifications over WebSocket
connections. Skydive support multiple graph backends for the Graph. The
backend will be always used by agents while the backend for analyzers can be
choosen. Each modification is kept in the datastore so that we have a full
history of the graph. This is really useful to troubleshoot even if
interfaces do not exist anymore.
Fill the graph with topology informations collected. Multiple probes fill the graph in parallel. As an example there are probes filling graph with network namespaces, netlink or OVSDB information.
Skydive keep a track of packets captured in flow tables. It allows Skydive to keep metrics for each flows. At a given frequency or when the flow expires (see the config file) flows are forwarded from agents to analyzers and then to the datastore.
Each time a new flow is received by the analyzer the flow is enhanced with topology informations like where it has been captured, where it originates from, where the packet is going to.
Flow probes capture packets and fill agent flow tables. There are different ways to capture packets like sFlow, afpacket, PCAP, etc.
Skydive uses Gremlin language as its graph traversal language. The Skydive Gremlin implementation allows to use Gremlin for flow traversal purpose. The Gremlin engine can either retrieve informations from the datastore or from agents depending whether the request is about something is the past or for live monitoring/troubleshooting.
Skydive uses Etcd to store API objects like captures. Agents are watching Etcd so that they can react on API calls.
This component watches Etcd and the graph in order to start captures. So when a new capture is created by the API on-demande probe looks for graph nodes matching the Gremlin expression, and if so, start capturing traffic.