fix(setup-dpdk): ip link down each NIC + mount hugetlbfs at /mnt/huge1g

[skullcrushercmd]

Summary

Two operator-side speedbumps surfaced on c6in.metal during anygpt-52 (PR #65 issuecomment-4339242358):

1. dpdk-devbind refuses to bind active interfaces:

Warning: routing table indicates that interface is active. Not modifying.

Operators had to ip link set <ifc> down on every NIC by hand before the bind succeeded.

2. Reserving 1 GiB hugepages was not enough for rte_eal_init:

EAL: No available 1048576 kB hugepages reported on node 0/1

Operators had to mount -t hugetlbfs -o pagesize=1G nodev /mnt/huge1g manually before the scanner could find the pages.

Fix

• bdf_to_iface() walks /sys/bus/pci/devices/<bdf>/net/ to map BDF → iface name. cmd_bind invokes ip link set <ifc> down on each target before invoking dpdk-devbind. Best-effort: missing ip, missing iface (already vfio-pci), and already-down ifaces all proceed to the bind.
• ensure_hugetlbfs_mount() mounts a hugetlbfs of the matching pagesize at the configured path after a successful nr_hugepages reservation. Default targets are /mnt/huge1g (1 GiB) and /mnt/huge2m (2 MiB); override via ANYSCAN_DPDK_HUGEPAGES_1G_MOUNT / _2M_MOUNT, or set to empty to opt out (operators provisioning hugetlbfs via fstab). Idempotent.
• ANYSCAN_DPDK_LOAD_ONLY=1 hook lets the test source the script without triggering its argv dispatch.

Test plan

• bash tools/test-setup-dpdk.sh — 9/9 pass
• cmd_bind invokes ip link set <ifc> down BEFORE dpdk-devbind --bind=vfio-pci (order verified by line numbers in a single cmd log)
• ensure_hugetlbfs_mount calls mount -t hugetlbfs -o pagesize=1G nodev <path>
• ensure_hugetlbfs_mount is no-op when target is already hugetlbfs with the matching pagesize
• ensure_hugetlbfs_mount is no-op with empty mount path
• bdf_to_iface resolution against a fake /sys tree (positive + negative)

🤖 Generated with Claude Code

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve empty mount override when reading env defaults

The script documents that operators can disable auto-mounting by setting ANYSCAN_DPDK_HUGEPAGES_1G_MOUNT / _2M_MOUNT to an empty string, but these assignments use ${VAR:-default} so an empty value is treated as unset and replaced with /mnt/huge1g or /mnt/huge2m. In practice, the opt-out path is unreachable and ensure_hugetlbfs_mount will still try to create/mount those paths, which can cause unwanted mount attempts on hosts where hugetlbfs is managed externally (e.g., via fstab).

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