ip6_tnl_xmit(9)

💖 ip6_tnl_xmit(9) 💖

hey bestie 🫶 welcome to the Kernel API Manual page for ip6_tnl_xmit — yes, the one and only. grab a strawberry 🍓 and let’s get into it.

✨ NAME ✨

ip6_tnl_xmit — encapsulate packet and send. literally does what it says, no cap.

🌸 SYNOPSIS 🌸

       int ip6_tnl_xmit (struct sk_buff *skb , struct net_device *dev , __u8
       dsfield , struct flowi6 *fl6 , int encap_limit , __u32 *pmtu , __u8
       proto );

🦋 ARGUMENTS 🦋

• skb — the outgoing socket buffer, aka the packet bestie being sent out.
• dev — the outgoing tunnel device.
• dsfield — dscp code for outer header.
• fl6 — flow of tunneled packet.
• encap_limit — encapsulation limit.
• pmtu — Path MTU is stored if packet is too big.
• proto — next header value.

🎀 DESCRIPTION 🎀

okay so this function builds a new header and does some sanity checks on the packet before sending it. that’s the whole routine: make the header, vibe-check the packet, send. iconic behavior honestly 💅

🔥 RETURN 🔥

• 0 — success, we love to see it.
• -1 — fail.
• -EMSGSIZE — message too big. return mtu in this case.

ngl, -EMSGSIZE is giving “packet too chunky for this path” 😭 and the mtu gets returned in this case.

💜 SEE ALSO 💜

Kernel file: ./net/ipv6/ip6_tunnel.c

• ip6_tnl_lookup(9)
• ip6_tnl_bucket(9)
• ip6_tnl_link(9)
• ip6_tnl_unlink(9)
• ip6_tnl_create(9)
• ip6_tnl_locate(9)
• ip6_tnl_dev_uninit(9)
• ip6_tnl_parse_tlv_enc_lim(9)
• ip6_tnl_addr_conflict(9)
• ip6_tnl_change(9)
• ip6_tnl_siocdevprivate(9)
• ip6_tnl_change_mtu(9)
• ip6_tnl_dev_setup(9)
• ip6_tnl_dev_init_gen(9)
• ip6_tnl_dev_init(9)
• ip6_fb_tnl_dev_init(9)
• ip6_tunnel_init(9)
• ip6_tunnel_cleanup(9)

that’s the page, bestie 🫶 this lil manual comes from ./net/ipv6 (source/version), dated October 2026, and it’s the ip6_tnl_xmit(9) page from the Kernel API Manual. periodt. 💜