# dnsmasq: busy loop in proxy DHCP with a tagged range

Found 2026-10-29 while testing Rollcall's proxy DHCP mode (gdb on a stuck lab
rack controller). Affects dnsmasq 2.91 (Debian 13) and 2.93 (latest release).
Rollcall works around it by leaving the tag off proxy ranges
(`cmd/rollcall/network.go`, `dnsmasqConfig`).

| File | |
|---|---|
| `report.txt` | the report to send upstream (plain text, patch inline) |
| `repro.sh` | reproducer: `sudo ./repro.sh /path/to/dnsmasq` (two netns + veth, two PXE DISCOVERs) |
| `0001-proxy-dhcp-reset-context-tags.patch` | one-line fix against 2.93, applies with `patch -p1` or `git apply` |

Results on a Debian 13 VM:

| dnsmasq | Configuration | CPU after two PXE requests |
|---|---|---|
| 2.91 (Debian) | tagged proxy range, `log-dhcp` | 100% |
| 2.93 | same | 100% |
| 2.93 + patch | same | 0% |
| 2.93 | no `log-dhcp`, `dhcp-option` for an absent tag | 69% |
| 2.93 + patch | same | 0% |

Status: not reported yet.