Virtual network interface multiplexing

A method, comprising:

• assigning, by one or more control-plane components of a virtual network interface multiplexing (VNIM) service, one or more virtual network interfaces (VNIs) as members of a first interface group, wherein a first VNI of the one or more VNIs is attached to a first compute instance, and wherein network traffic directed to a particular client-accessible service endpoint address (CSEA) associated with the first interface group is to be distributed among members of the first interface group by a first client-side component of the VNIM service;
• propagating, by the one or more control plane components, membership metadata of the first interface group to one or more client-side components including the first client-side component;
• and
• in response to detecting, by the first client-side component, that a baseline network packet generated at a particular traffic source is directed to the particular C SEA,
• identifying, by the first client-side component, the first VNI as a destination for contents of the baseline network packet;
• and
• selecting, by the first client-side component, based at least in part on connection state information generated as a result of said identifying, the first VNI as a destination for a subsequent baseline packet directed to the particular CSEA from the particular traffic source.

A non-transitory computer-accessible storage medium storing program instructions that when executed on one or more processors implements a control-plane component of a virtual network interface multiplexing (VNIM) service, wherein the control-plane component is configured to:

• assign a plurality of virtual network interfaces (VNIs) as members of a first interface group, wherein a first VNI of the plurality of VNIs is attached to a first compute instance, and wherein network traffic directed to a particular endpoint address associated with the first interface group is to be distributed among members of the first interface group by a first client-side component of the VNIM service;
• identify one or more client-side components configured to distribute the network traffic among the members of the first interface group in accordance with membership metadata of the first interface group, wherein the one or more client-side components include the first client-side component, and wherein the membership metadata indicates the plurality of VNIs that are members of the first interface group;
• propagate the membership metadata of the first interface group to the one or more identified client-side components;
• and
• in response to a detection of an unhealthy state of the first compute instance:
• detach the first VNI from the first compute instance, wherein, in response to detaching the first VNI from the first compute instance, network packets from the one or more identified client-side components and directed to the first VNI are not received at the first compute instance;
• and
• attach the first VNI to a different compute instance, wherein, in response to attaching the first VNI to the different compute instance, network packets from the one or more identified client-side components and directed to the first VNI are received at the different compute instance.