Why does hijack accept non-LKL fds? about linux HOT 2 CLOSED

there are a couple of use cases.

• if an application opens a socket but also open a file (like stdin and stdout), the lib should distinguish and dispatch them
• if liblkl{.a,.so} (or linked library) uses system calls and linked with libhijack, then libhijack should treat those system calls goes to the host calls. virtio network backend (currently only with tap) required such a behavior
  • the tap case is easy to mitigate as the code is just a couple of lines, but if we depend on an external library (I'm thinking dpdk in my mind), it would be more complicated

so notifying something to callers is not always happy for users.

I would say if applications need to only use LKL syscalls, the hijack library is not for them: call LKL syscall directly.

see more detail discussion in the Section "3.13.6 System Call Hijacking" of rumpkernel book (https://github.com/rumpkernel/book).

I understand handling host fds in hijack library is broken and I haven't come up with a perfect solution. and I'm so reluctant to spend more time for hijack library (because of such limitations).
but the library is only there because of the instant use case to benefit LKL with existing application binaries.

from linux.

Got it, very helpful explanation, thanks!

from linux.