====targetcli-fb====
  * it needs to be turned on in the kernel. drivers -> Infiniband -> SRP
  * turn on both target and initiator please
  * in targetcli, /srpt is the relevant path
  * targets are formatted like ib.fe80000000000000f4521403002c18b1
  * idk how you get those numbers except to examine an ipoib link, such as:

  5: ib0: <...> mtu 2044 ...
      link/infiniband 80:00:02:18:fe:80:00:00:00:00:00:00:f4:52:14:03:00:2c:18:b1
      brd             00:ff:ff:ff:ff:12:40:1b:ff:ff:00:00:00:00:00:00:ff:ff:ff:ff

Now strip the first 4 bytes off (they change anyway) and remove the :'s

  fe800000000000005849560e59150301

The top 64 bits of the ACL might need to be 0 or they might be the same as the GUID; I don't know the initiator ID actually gets generated and I'm not doing any more digging into it.

  /srpt> ib.fe800000000000005849560e53b70b01/acls create ib.00000000000000005849560e59150301
  Created Node ACL for ib.00000000000000005849560e59150301
  Created mapped LUN 0.

A Linux SRP target is always visible from all InfiniBand partitions. That limits its usefulness to me.

====Dependencies====

  apt install srptools

Find targets to connect to:

    # srp_daemon -o -v -c -p 1

  * -o means "run once" otherwise dmesg on all your hosts will get polluted with SRP login noise.
  * -v means "say what you're doing"
  * -c means "emit target information in a format we can use later"
  * -p 1 means "only scan on HCA port 1" so obviously change this if you are initiating from port 2...

Lazy benchmarking seems good:

  [root]@[shark][~]# dd if=/dev/sdb of=/dev/null bs=4M
  4096+0 records in
  4096+0 records out
  17179869184 bytes (17 GB, 16 GiB) copied, 5.38771 s, 3.2 GB/s
  
  [root]@[shark][~]# dd if=/dev/zero of=/dev/sdb bs=4M
  dd: error writing '/dev/sdb': No space left on device
  4097+0 records in
  4096+0 records out
  17179869184 bytes (17 GB, 16 GiB) copied, 13.7431 s, 1.3 GB/s

...so I'm using some for swap. We'll see how long it takes me to induce a kernel panic. ;)