bpf: Add bpf_strncmp helper
#871
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The `bpf_strncmp` helper allows for better string comparison in eBPF programs. Kernel patchset: https://lore.kernel.org/bpf/20211210141652.877186-1-houtao1@huawei.com/
| let dst = unsafe { ptr.as_mut() }; | ||
| let TestResult(dst_res) = dst.ok_or(-1)?; | ||
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| let cmp_res = bpf_strncmp(str_bytes, c"fff"); |
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@alessandrod Are you fine with using CStr literals here? I had a bit of dilemma, since their stabilization goes slow. The other alternative could be using byte literals and forcing people to null terminate them.
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I think the literal is fine, but both arguments should be &CStr?
| /// } | ||
| /// ``` | ||
| #[inline] | ||
| pub fn bpf_strncmp(s1: &[u8], s2: &CStr) -> Ordering { |
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I don't understand the API why one is a slice and the other is &CStr?
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Well, the most common way of using bpf_strncmp I've seen (and I'm doing in my projects 😛 ) is comparing a string we got from bpf_probe_read_user_str_bytes (which returns a byte slice) with some literal written in the program (where the CStr literal is very handy).
But yeah, I get your point about consistency. Since our whole bpf_probe_read_*_bytes API returns byte slices, I see two solutions:
- We just use byte slices. And tell people to use byte literals - I'm mostly convinced to that so far.
- We make everything return CStr - but nah, we would need to care about null termination checks and so.
So let's maybe make both &[u8]
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@vadorovsky, this pull request is now in conflict and requires a rebase. |
The
bpf_strncmphelper allows for better string comparison in eBPF programs.Kernel patchset:
https://lore.kernel.org/bpf/20211210141652.877186-1-houtao1@huawei.com/