Techniques are provided to decouple service chain structure from the underlying network forwarding state and allow for data plane learning of service chain forwarding requirements and any association between services function state requirements and the forward and reverse forwarding paths for a service chain. In a network comprising a plurality of network nodes each configured to apply a service function to traffic that passes through the respective network node, a packet is received at a network node. When the network node determines that the service function it applies is stateful, it updates context information in a network service header of the packet to indicate that the service function applied at the network node is stateful and that traffic for a reverse path matching the classification criteria is to be returned to the network node.