ieee80211_ra...terator_init(9)

💅 ieee80211_radiotap_iterator_init — radiotap parser iterator initialization

okay so bestie, this one's from the Kernel API Manual, page ieee80211_ra...terator_init(9), and it's literally the glow-up ritual for your radiotap parser iterator. let's get into it 💖

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✨ NAME ✨

ieee80211_radiotap_iterator_init — radiotap parser iterator initialization

like. the setup. the origin story. the "get your iterator ready before the real work starts" moment 🎀

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🦋 SYNOPSIS 🦋

int ieee80211_radiotap_iterator_init (struct ieee80211_radiotap_iterator
*iterator , struct ieee80211_radiotap_header *radiotap_header , int
max_length , const struct ieee80211_radiotap_vendor_namespaces *vns );

no cap, that's the whole signature. four args, one int coming back at you 💫

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🌸 ARGUMENTS 🌸

• iterator — the radiotap_iterator you're initializing. this is the main character of the whole operation, honestly 👑
• radiotap_header — the radiotap header you're going to parse. the thing being read. iconic.
• max_length — total length we can parse into (eg, whole packet length). like, how far you're allowed to go 🫶
• vns — vendor namespaces to parse. the little namespace situation 💜

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🔥 RETURN 🔥

0 or a negative error code if there is a problem.

that's it. 0 = slay, negative = uh oh 😭

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⭐ DESCRIPTION ⭐

So this function initializes an opaque iterator struct which can then be passed to ieee80211_radiotap_iterator_next to visit every radiotap argument which is present in the header. It knows about extended present headers and handles them. fr fr, it's got you on the extended-present-header front — no manual fiddling required ✨

🧚 how to use it, bestie

1. call __ieee80211_radiotap_iterator_init to init a semi-opaque iterator struct ieee80211_radiotap_iterator (no need to init the struct beforehand) checking for a good 0 return code.
2. then loop calling __ieee80211_radiotap_iterator_next... it returns either 0, -ENOENT if there are no more args to parse, or -EINVAL if there is a problem.

the iterator's this_arg member points to the start of the argument associated with the current argument index that is present, which can be found in the iterator's this_arg_index member. This arg index corresponds to the IEEE80211_RADIOTAP_... defines. iykyk 💅

🎀 radiotap header length

You can find the CPU-endian total radiotap header length in iterator->max_length after executing ieee80211_radiotap_iterator_init successfully. so like, once it actually works, the length's right there waiting for you 💖

⚠️ Alignment Gotcha

You must take care when dereferencing iterator.this_arg for multibyte types... the pointer is not aligned. Use get_unaligned((type *)iterator.this_arg) to dereference iterator.this_arg for type "type" safely on all arches.

not me warning you twice: the pointer is not aligned, bestie. do not just cast and deref like it's nothing. get_unaligned is the safe route on all arches, periodt 🙈

🍓 example code

See Documentation/networking/radiotap-headers.rst — go look, it's giving tutorial energy 🌈

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🌟 SEE ALSO 🌟

• Kernel file ./net/wireless/radiotap.c
• ieee80211_radiotap_iterator_next(9)

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okay that's the whole page 🫶 this gem lives in ./net/wireless, dated October 2026, and it's from the Kernel API Manual — version vibes: ieee80211_ra...terator_init(9). go init that iterator, bestie, you're gonna eat 💜💫