Linux network namespaces allow separate networking environment for a group of processes (sharing uid or from a separate user).
DNS settings (/etc/resolv.conf) is however shared between all those environments, which provides certain inconvenience.
Typically (i.e. in ip netns tool) mount (filesystem) namespace is used along with netns as a workaround, mapping distinct /etc/netns/... files to main /etc/resolv.conf. This tool provides different approach based on a FUSE filesystem which provides this mapping without using additional mount namespaces.
It works by inspecing PIDs of each programs that access the mounted /etc/resolv.conf, using /proc/<pid>/ns/net to find out which underlying file should be used and forwarding reads and writes to that file instead. Missing files may be propagated from a user-specified template file.
(untested)
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Download a pre-built x64_64 version from Github releases or try cargo install or download source code and use cargo build --release. Copy resulting executable where you want.
Integrating the tool with distro's networking stack is out of scope for this document.
``` resolvconffs --help Usage: /opt/resolvconffs [OPTIONS]
Special FUSE filesystem that maps its sole file to other files based on network namespace of process that queries the file.
Positional arguments: backingdirectory Directory where to look for resolv.conf-like files for each netns. mountpointfile
Optional arguments:
-h, --help
-p, --extension EXTENSION Filename extension. resolvconffs maps its file to
The project is not libified and library usage is not intended.
There is simple reusable component named FileMapperFs inside, allowing implementing similar single-file filesystems based on fuser crate that maps the file based on uid, gid or pid of accessing process.