IP_TOS(2const)

💖 IP_TOS — type of service 💖

okay bestie, welcome to the IP_TOS(2const) page, she's short, she's iconic, she's the one who decides how fancy your packets get to act on the network 🌈✨

This one lives in the Standard C library (libc, -lc), just so you know where to send the vibes 🫶

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✨ SYNOPSIS ✨

#include <netinet/in.h>  /* Definition of IP* constants */
#include <sys/socket.h>

int setsockopt(int sockfd, IPPROTO_IP, IP_TOS,
               const int *tos, sizeof(int));
int getsockopt(int sockfd, IPPROTO_IP, IP_TOS,
               int *tos, sizeof(int));

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💅 DESCRIPTION 💅

So basically, IP_TOS lets you set or receive the Type-Of-Service (TOS) field that gets sent along with every single IP packet that originates from this socket 👑. What is it for? Prioritizing packets on the network, periodt.

There's a little roster of standard TOS flags defined for you, and honestly? They ate:

• IPTOS_LOWDELAY — to minimize delays for interactive traffic,
• IPTOS_THROUGHPUT — to optimize throughput,
• IPTOS_RELIABILITY — to optimize for reliability,
• IPTOS_MINCOST — should be used for "filler data" where slow transmission doesn't matter.

⚠️ okay listen up, this part is important: at most one of these TOS values can be specified. Other bits are invalid and shall be cleared. No mix-and-matching, bestie, that's not the move 💀

Linux sends IPTOS_LOWDELAY datagrams first by default, but fr fr, the exact behavior depends on the configured queueing discipline. So it's giving "defaults to main character, but the queue decides the plot" 🎀

Alsooo, some high-priority levels may require superuser privileges (the CAP_NET_ADMIN capability). So don't be shocked if you need the fancy permissions ✨

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😭 ERRORS 😭

See IPPROTO_IP(2const). See setsockopt(2). See ip(7). (yeah she's pointing you at her friends, that's the whole section, no notes 💜)

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🌸 HISTORY 🌸

• Linux 1.0. — she's been here since basically forever, lowkey a legend 🦋

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🧚 SEE ALSO 🧚

• IPPROTO_IP(2const)
• setsockopt(2)
• ip(7)

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that's the whole page, bestie, you understood it perfectly, i'm so proud of you 🥹💖 go set some TOS bits responsibly, mwah 💅✨ from the Linux man-pages 6.20, dated 2025-11-25 🎀🫶