ip6_sk_dst_lookup_flow(9)

💅 ip6_sk_dst_lookup_flow(9) — like, the Kernel API Manual entry you actually wanna read ✨

okay so bestie, welcome to the glow-up of ip6_sk_dst_lookup_flow(9) from the Kernel API Manual. this is the function that does a socket-cached route lookup on a flow, and honestly? it's giving main character energy in net/ipv6. let's get into it 🎀

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✨ NAME ✨

ip6_sk_dst_lookup_flow — performs a socket cached route lookup on a flow 💫

like literally, that's the whole vibe. socket. cached route. flow. slay.

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🌸 SYNOPSIS 🌸

struct dst_entry * ip6_sk_dst_lookup_flow (struct sock *sk , struct
flowi6 *fl6 , const struct in6_addr *final_dst , bool connected );

no cap, that's the exact signature — don't @ me, copy it character for character 🫶

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🦋 ARGUMENTS 🦋

• sk — the socket that provides the dst cache and route info. she's the one holding the goods 💖
• fl6 — the flow to lookup. this is what we're out here looking up, periodt.
• final_dst — the final destination address, specifically for the ipsec lookup. iykyk 🔥
• connected — whether sk is connected or not. a little bool that changes everything, ngl.

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👑 DESCRIPTION 👑

so here's the tea ☕ — this function performs a route lookup on the given flow, with the possibility of using the cached route in the socket if it is valid. she's efficient like that 💅

it will take the socket dst lock when operating on the dst cache. and because of that lock situation:

⚠️ as a result, this function can only be used in process context. do not try this from anywhere else, bestie, i'm serious 😭

in addition (and this is the cute extra bit 🌈), for a connected socket, it caches the dst in the socket if the current cache is not valid. very "if it doesn't fit, fix it" of her.

and what does it return? a valid dst pointer on success 🎉 — or a pointer encoded error code 💀. like, it's either a win or an error hidden inside a pointer. choose your fighter.

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🧚 SEE ALSO 🧚

• Kernel file ./net/ipv6/ip6_output.c ip6_dst_lookup(9)
• ip6_dst_lookup_flow(9)

go read those too fr fr, they're the supporting cast and they ate ✨

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and that's the whole page, bestie — no notes, she's iconic 💜

this little sign-off comes straight from ./net/ipv6, dated October 2026 — catch you on the next lookup, mwah 🍓💖