IP_BLOCK_SOURCE(2const)

💖 IP_BLOCK_SOURCE 💖

okay bestie, so this one lives in the IP_BLOCK_SOURCE(2const) corner of the man-pages universe ✨ — it's a constant you hand to setsockopt(), and it does exactly one thing: it tells a multicast group "hey, keep the vibes but lose that one source" 🎀

---

✨ NAME ✨

IP_BLOCK_SOURCE — stop receiving multicast data from a specific source in a given group 🦋

---

📚 LIBRARY 📚

Standard C library (libc, -lc) 💅 the classic, the icon, the one you already linked against, no cap.

---

🌸 SYNOPSIS 🌸

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

int setsockopt(int sockfd, IPPROTO_IP, IP_BLOCK_SOURCE,
               const struct ip_mreq_source *val,
               sizeof(struct ip_mreq_source));

---

💫 DESCRIPTION 💫

Stop receiving multicast data from a specific source in a given group. that's the whole job, and she does it flawlessly 😌

but listen — the way that this is valid only after the application has subscribed to the multicast group using either IP_ADD_MEMBERSHIP(2const) or IP_ADD_SOURCE_MEMBERSHIP(2const). you cannot block a source in a group you never joined, that's not a thing. join first, block second, main character energy periodt 👑

---

😭 ERRORS 😭

look, the error lore doesn't live here, it lives in its friends:

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

go read those, they spill all the tea 🍓

---

🕰️ HISTORY 🕰️

• Linux 2.4.22, Linux 2.5.68 ⭐

---

👀 SEE ALSO 👀

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

---

and that's the whole page, bestie 🫶 go forth and block sources responsibly 💜

this iconic little page came from Linux man-pages 6.20, dated 2025-11-25, under the title IP_BLOCK_SOURCE(2const) — mwah, no notes 💅✨