feat(bpf): implement allow_ethertype L2 gatekeeper#51
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leodido wants to merge 8 commits intofeat/multi-value-rodatafrom
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feat(bpf): implement allow_ethertype L2 gatekeeper#51leodido wants to merge 8 commits intofeat/multi-value-rodatafrom
allow_ethertype L2 gatekeeper#51leodido wants to merge 8 commits intofeat/multi-value-rodatafrom
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L2 EtherType allowlist program. Reads eth->h_proto and checks it against a configurable set of allowed EtherTypes. Drops frames with non-matching EtherTypes (TC_ACT_SHOT). Fail-closed on truncated Ethernet headers. Rodata: allowed[MAX_MULTI_VALUES] array + num_allowed count + slot for chain tail-calls. In standalone mode, bpf_tail_call silently fails and falls through to TC_ACT_OK. Also adds ETH_P_IPV6, ETH_P_ARP, and MAX_MULTI_VALUES defines to commons.bpf.h. Co-authored-by: Ona <no-reply@ona.com>
Add case program_allow_ethertype in parse_input() calling the existing
parse_ethertypes() helper. Add allow_ethertype to program_requires_input().
Add allow_ethertype to input_fields in api.lua as the first multi-value
entry: { field = "ethertypes", multi = true }.
Co-authored-by: Ona <no-reply@ona.com>
Add case program_allow_ethertype in load_chain_program(). Passes the full ethertypes struct (values[] + count) to set_chain_rodata(). Add allow_ethertype to program_supports_chaining(). Co-authored-by: Ona <no-reply@ona.com>
Flag tests (cli.flags.bats): - missing input, unknown name, invalid hex, duplicate values, trailing +, leading + Integration tests (cli.bats): - allow_ethertype ipv4+arp allows IPv4 ping (needs ARP + IPv4) - allow_ethertype ipv6 blocks IPv4 ping (IPv4 not in allowed set) - chain allow_ethertype:ipv4+arp,allow_ipv4:ADDR allows matching traffic CNI test (cni.bats): - allow_ethertype via CNI with ipv4+arp fixture Co-authored-by: Ona <no-reply@ona.com>
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allow_ethertype L2 gatekeeper
Co-authored-by: Ona <no-reply@ona.com>
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__u8 overflows at 256. If MAX_MULTI_VALUES were ever increased beyond 255, the loop would never terminate. __u32 is safer and has no performance cost in BPF. Co-authored-by: Ona <no-reply@ona.com>
Add flag tests for consecutive ++ delimiter, too many values exceeding MAX_MULTI_VALUES, and zero hex value 0x0000. Fix missing trailing newlines in both test files. Add integration tests for chain blocking non-matching EtherType and for hex value input (0x0800+0x0806). Co-authored-by: Ona <no-reply@ona.com>
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- Fix bpf_printk NDEBUG macro: use do { } while(0) instead of
{ } while(0) to avoid dangling-else in unbraced if/else.
- Update standalone template comment to reflect multi-value rodata
and the slot default-zero contract.
- Add cross-representation duplicate test (ipv4+0x0800).
- Add integration test: allow_ethertype ipv4 without ARP blocks ping
(verifies ARP filtering at L2).
- Document chain ordering constraint: allow_ethertype must be first
because L3+ passthrough paths bypass downstream L2 filters.
- Document VLAN (802.1Q) limitation in both README.txt and docs.
Co-authored-by: Ona <no-reply@ona.com>
Fix bpf_printk no-op macro to use do { } while(0). The previous
{ } while(0) form causes a dangling-else compile error when used
in unbraced if/else blocks.
Document allow_ethertype chain ordering constraint: must be first
in a chain because L3+ programs pass through non-matching traffic
via TC_ACT_OK, bypassing downstream L2 filters. Document 802.1Q
VLAN limitation (outer EtherType is 0x8100, not the payload type).
Add test for cross-representation duplicate detection (ipv4+0x0800).
Add integration test verifying that allow_ethertype ipv4 without arp
blocks ping (ARP resolution fails at L2).
Update standalone template comment to reflect multi-value rodata
layout and the slot default-zero contract.
Co-authored-by: Ona <no-reply@ona.com>
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fntlnz
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May 4, 2026
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L2 EtherType allowlist program. Drops Ethernet frames whose EtherType
is not in the allowed set. Accepts a
+-delimited list of symbolicnames (
ipv4,ipv6,arp) or0x-prefixed hex values.First multi-value input program, using the infrastructure from PR #49.
Changes
BPF program (
bpf/allow_ethertype.bpf.c): readseth->h_proto,linear scans
allowed[MAX_MULTI_VALUES]array. Match: tail-call next.No match:
TC_ACT_SHOT. Fail-closed on truncated Ethernet headers.Also adds
ETH_P_IPV6,ETH_P_ARP,MAX_MULTI_VALUEStocommons.bpf.h.Parser wiring:
case program_allow_ethertypeinparse_input()calling the existing
parse_ethertypes()helper. Added toprogram_requires_input().input_fieldsentry inapi.lua:{ field = "ethertypes", multi = true }.Chain loader:
case program_allow_ethertypeinload_chain_program(). Passes the full ethertypes struct (array + count)to
set_chain_rodata(). Added toprogram_supports_chaining().Tests: 6 flag validation tests (missing input, unknown name, invalid
hex, duplicates, trailing/leading
+). 3 integration tests (standaloneallow, standalone block, chain). 1 CNI test with fixture.
Docs:
README.txtanddocs/README.md.Stacked on
feat/multi-value-rodata) - multi-value input infrastructurefeat/dispatcher-chain) - chain CLIfeat/dispatcher-bpf) - dispatcher infrastructureallow_dnsprogram #43 (feat/allow-dns)allow_portprogram #42 (feat/allow-port)allow_ipprogram #41 (feat/allow-ip)