[ofa-general] Question about rdma_cm

[Sean Hefty]

>Thanks for your answer.
>I saw the DGID to path/LID earlier, but I didn't see where and how
>exactly the GID is obtained.

If you're tracing through the code, look at rdma_resolve_addr() calling
rdma_resolve_ip().  The latter is in the ib_addr module (addr.c).
rdma_resolve_ip() calls addr_resolve_remote() and addr_send_arp().

>I also saw how the GID is obtained from the L2-like address, but I'm
>still not sure how the L2-like address is obtained.
>Is there an ARP like protocol implemented on IB?

yes - For IPoIB to communicate with a remote system, it needs to map the
destination IP address to a usable IB address (DGID, PKey, QPN), plus perform a
path record query to get the LIDs.  The rdma cm follows the same concept and
relies on the network stack to provide it with the correct information.

- Sean