RDMA_RESOLVE_ADDR(3)

💖 RDMA_RESOLVE_ADDR(3) 💖

okay bestie, welcome to the Librdmacm Programmer's Manual entry for rdma_resolve_addr — yes that's the whole title, RDMA_RESOLVE_ADDR(3), and no we are not skipping any of it. 🎀

✨ NAME ✨

rdma_resolve_addr — resolve destination and optional source addresses. that's it, that's the vibe. 🦋

✨ SYNOPSIS ✨

#include <rdma/rdma_cma.h>

int rdma_resolve_addr (struct rdma_cm_id *id, struct sockaddr *src_addr,
struct sockaddr *dst_addr, int timeout_ms);

look at her. so clean. so iconic. 👑

✨ ARGUMENTS ✨

• id — the RDMA identifier. your main character. 💅
• src_addr — source address information. this one is allowed to be NULL, she's optional, she's lowkey mysterious. 🌸
• dst_addr — destination address information. this one? required. no skipping. ✨
• timeout_ms — how long you're willing to wait for resolution to finish. the patience budget, fr fr. ⏳

✨ DESCRIPTION ✨

so what she does is resolve destination and optional source addresses from IP addresses to an RDMA address. that's the whole job. and if it goes well? the rdma_cm_id you passed in gets bound to a local device. slay. 💖

✨ RETURN VALUE ✨

• 0 on success — ate, no crumbs. 🎀
• -1 on error — and if that happens, errno gets set to tell you why. she's not gonna leave you guessing. 😭

✨ NOTES ✨

okay so the tea: this call is what you use to map a given destination IP address to a usable RDMA address. 🗺️

the IP-to-RDMA mapping happens using the local routing tables, or via ARP. iykyk.

here's the part you actually need to remember:

• if a source address is given, the rdma_cm_id is bound to that address — exactly the same as if rdma_bind_addr had been called. same energy, different function name. ✨
• if no source address is given, and the rdma_cm_id hasn't been bound to a device yet, then the rdma_cm_id gets bound to a source address based on the local routing tables. the routing tables decide. they're the group chat admin here. 💀
• after this call, the rdma_cm_id will be bound to an RDMA device. periodt. 🔥

and like, when do you even call this? typically from the active side of a connection, before you call rdma_resolve_route and rdma_connect. it's giving "step one of the whole ritual". 🧚

✨ INFINIBAND SPECIFIC ✨

for the InfiniBand girlies: this call maps the destination — and, if given, the source — IP addresses to GIDs. 🌈

heads up bestie: in order to do that mapping, IPoIB must be running on both the local and remote nodes. both. not one. both. 🙈

✨ SEE ALSO ✨

• rdma_create_id(3)
• rdma_resolve_route(3)
• rdma_connect(3)
• rdma_create_qp(3)
• rdma_get_cm_event(3)
• rdma_bind_addr(3)
• rdma_get_src_port(3)
• rdma_get_dst_port(3)
• rdma_get_local_addr(3)
• rdma_get_peer_addr(3)

the whole squad, assembled. 🫶

librdmacm · 2007-10-31 · and that's the RDMA_RESOLVE_ADDR(3) page, mwah 💋 go resolve something, bestie. 💜