feat: flip swap mechanism — MD as primary, RST as override (Phase 1)

This is the first of three phases inverting the per-page swap mechanism
so MD becomes the canonical primary and RST becomes the rare override.

Phase 1 — file renames + conf.py exclude_patterns flip only:
- Rename docs/**/md-<stem>.md to docs/**/<stem>.md (drop md- prefix)
  for all 254 stems previously listed in docs/_swap.txt
- Rename docs/**/<stem>.rst to docs/**/rst-<stem>.rst (add rst- prefix)
  for the same 254 stems
- Repurpose docs/_swap.txt as docs/_rst_overrides.txt; initially empty
  comment-only since no pages need the RST fallback right now
- conf.py exclude_patterns flipped: rst-*.rst is now excluded by default
  instead of md-*.md
- conf.py runtime-artifact references updated to _rst_override_state.json
  and _md_exclude.txt (Phase 2 will rewrite swap_sources.py to produce
  these names; for now no swap script runs because overrides list is empty)

Phase 2 (next commit on this branch) will rewrite scripts/swap_sources.py
with inverted rename direction, delete scripts/import_myst.py + tests, and
update tests/test_swap_sources.py for the new semantics.

Phase 3 will be the cleanup pass and ready-for-review flip.

Generated by robots https://vyos.io

1 files changed, 42 insertions, 0 deletions

diff --git a/docs/vpp/limitations.md b/docs/vpp/limitations.md
new file mode 100644
index 00000000..9582347a
--- /dev/null
+++ b/docs/vpp/limitations.md
@@ -0,0 +1,42 @@
+---
+lastproofread: '2026-02-17'
+---
+
+(vpp-limitations)=
+
+```{include} /_include/need_improvement.txt
+```
+
+# VPP Dataplane Limitations
+
+VPP Dataplane provides significant performance advantages, but has some
+limitations you should consider.
+
+- **Feature Parity**
+
+  VPP does not support all features available in the Linux kernel dataplane.
+  Some networking features, specific protocols, or services may not be
+  available.
+
+  While VPP supports various interface types similar to the kernel, their
+  capabilities may differ.
+
+- **NIC and Driver Compatibility**
+
+  VyOS currently supports only DPDK drivers for network interfaces.
+  Not all network interface cards are compatible with DPDK drivers.
+
+- **Data Path Limitations**
+
+  If a feature exists only in the kernel dataplane, traffic that uses that
+  feature cannot traverse VPP interfaces. Examples include:
+
+  - Firewall
+  - QoS
+
+  When traffic uses the pure VPP path, it does not reach the kernel, where
+  such features are implemented. Plan how traffic flows through your VyOS
+  instance to ensure it reaches the necessary features.
+
+  VPP provides native alternatives for some features. For example, VPP
+  native ACLs provide basic firewall functionality.