IFQ_DEQ_BEGIN(9)

okay so bestie, welcome to IFQ_DEQ_BEGIN(9) from the Kernel Developer's Manual — this is the page about dequeuing an mbuf from an interface sending queue. let's get into it 💅✨

🌸 NAME 🌸

ifq_deq_begin, ifq_deq_commit, ifq_deq_rollback — dequeue an mbuf from an interface sending queue 🎀

✨ SYNOPSIS ✨

#include <net/if_var.h>

struct mbuf *
ifq_deq_begin(struct ifqueue *ifq);

void
ifq_deq_commit(struct ifqueue *ifq, struct mbuf *m);

void
ifq_deq_rollback(struct ifqueue *ifq, struct mbuf *m);

💖 DESCRIPTION 💖

okay so the ifq_deq_* set of functions provides a non-atomic alternative to ifq_dequeue(9). 🫶

🚨 real talk: their use is discouraged — code should use ifq_dequeue(9) whenever possible. no cap.

• ifq_deq_begin(struct ifqueue *ifq) — get a reference to the next mbuf to be transmitted from the ifq interface send queue. if an mbuf is to be transmitted, also acquire a lock on the send queue to exclude modification or freeing of the referenced mbuf. its packet header must not be modified until the mbuf has been dequeued with ifq_deq_commit(). 🔒
• ifq_deq_commit(struct ifqueue *ifq, struct mbuf *m) — dequeue the mbuf m that was referenced by a previous call to ifq_deq_begin() and release the lock on ifq. ✅
• ifq_deq_rollback(struct ifqueue *ifq, struct mbuf *m) — release the lock on the interface send queue ifq that was acquired while a reference to m was being held. ↩️

🧚 CONTEXT 🧚

ifq_deq_begin(), ifq_deq_commit(), and ifq_deq_rollback() can be called during autoconf, from process context, or from interrupt context. 🌀

⭐ RETURN VALUES ⭐

ifq_deq_begin() returns the next mbuf to be transmitted by the interface. if no packet is available for transmission, NULL is returned. 🫡

🦋 SEE ALSO 🦋

• ifq_dequeue(9) 👀

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xoxo, Debian 💖 — March 20, 2021 ✨