bpf: policy: fix handling of ICMPv6 packet with extension headers #24797
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After walking the IPv6 extension headers, ipv6_hdrlen() returns the L4 proto type in `nexthdr` parameter. If we pass in a pointer to the IPv6 header's nexthdr field, then the actual packet content is changed and subsequent processing of the packet is broken (because we treat the first IPv6 extension header as an ICMPv6 header). So even if we don't care about the L4 proto type (because we already know that it's ICMPv6), we still need to provide some stack space to store the `nexthdr`. This only becomes relevant when ENABLE_ICMP_RULE is set, which is currently controlled by a hidden agent flag. Fixes: d49311c ("policy: Add bpf ICMP policy support with the "ENABLE_ICMP_POLICY" flag") Signed-off-by: Julian Wiedmann <jwi@isovalent.com>
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ha, completely missed that (and doesn't make sense at all to me 😺). Thanks! |
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It's a new beta feature, so we want to be able to disable it in user environments if there's a regression affecting more than just the ICMP policies. Long term, we want it to be always enabled, like other network policy features (e.g., deny policies). Also worth noting that this feature wasn't enabled until recently (unsure which exact version) because it was affected by a complexity issue before then. |
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Removing from v1.11 backports given it conflicts and ICMP policies were disabled there. |
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After walking the IPv6 extension headers, ipv6_hdrlen() returns the L4 proto type in
nexthdrparameter. If we pass in a pointer to the IPv6 header's nexthdr field, then the actual packet content is changed and subsequent processing of the packet is broken (because we treat the first IPv6 extension header as an ICMPv6 header).So even if we don't care about the L4 proto type (because we already know that it's ICMPv6), we still need to provide some stack space to store the
nexthdr.This only becomes relevant when ENABLE_ICMP_RULE is set, which is currently controlled by a hidden agent flag.
Fixes: d49311c ("policy: Add bpf ICMP policy support with the "ENABLE_ICMP_POLICY" flag")