SLIP and CSLIP serial-line IP networking
Carries IP packets over a plain serial line such as a UART or RS-232 link, using either classic SLIP or the header-compressed CSLIP variant. It was the standard way to dial into the internet in the late 1980s and early 1990s before PPP took over, and it survives today mainly on microcontrollers and other small embedded systems where its tiny framing overhead is attractive.
recommendation
Worth keeping but documenting as legacy because SLIP is a thin protocol layer over ordinary serial ports rather than a driver for obsolete hardware, and it still sees real upstream maintenance (a slab-out-of-bounds fix landed in April 2026). New serial-to-IP links should use PPP instead, but small embedded and microcontroller setups still rely on SLIP for its minimal overhead, so removal would be premature.
repository signals
sources
- lore.kernel.org
`drivers/net/slip/slip.c` received a targeted slab-out-of-bounds fix on 2026-04-15, so the code is still seeing non-trivial upstream maintenance.
- cateee.net
`CONFIG_SLIP` is still present in current kernel series, and the Kconfig help describes PPP as the more common protocol for the same serial-IP use case.
- en.wikipedia.org
SLIP has largely been replaced by PPP on PCs, but it still has niche use on microcontrollers because of its very small overhead.
codex reasoning notes (technical)
This is a real driver directory: `slip.c` implements the SLIP line discipline and `slhc.c` provides CSLIP header compression helpers. Evidence came from local `rg` inspection of `drivers/net/slip`, `lore_file_timeline` on `drivers/net/slip/slip.c`, and one web search that surfaced the LKDDb and Wikipedia URLs above. The lore evidence shows current maintenance rather than abandonment, while the deployment evidence points to a legacy/embedded niche rather than broad new deployments. Because SLIP is protocol glue over still-sold generic serial hardware, not a dead chipset, removal would be premature; annotate as legacy and prefer PPP for new serial-IP links.