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[ Upstream commit2cc74e1ee3] ROCE uses IGMP for Multicast instead of the native Infiniband system where joins are required in order to post messages on the Multicast group. On Ethernet one can send Multicast messages to arbitrary addresses without the need to subscribe to a group. So ROCE correctly does not send IGMP joins during rdma_join_multicast(). F.e. in cma_iboe_join_multicast() we see: if (addr->sa_family == AF_INET) { if (gid_type == IB_GID_TYPE_ROCE_UDP_ENCAP) { ib.rec.hop_limit = IPV6_DEFAULT_HOPLIMIT; if (!send_only) { err = cma_igmp_send(ndev, &ib.rec.mgid, true); } } } else { So the IGMP join is suppressed as it is unnecessary. However no such check is done in destroy_mc(). And therefore leaving a sendonly multicast group will send an IGMP leave. This means that the following scenario can lead to a multicast receiver unexpectedly being unsubscribed from a MC group: 1. Sender thread does a sendonly join on MC group X. No IGMP join is sent. 2. Receiver thread does a regular join on the same MC Group x. IGMP join is sent and the receiver begins to get messages. 3. Sender thread terminates and destroys MC group X. IGMP leave is sent and the receiver no longer receives data. This patch adds the same logic for sendonly joins to destroy_mc() that is also used in cma_iboe_join_multicast(). Fixes:ab15c95a17("IB/core: Support for CMA multicast join flags") Link: https://lore.kernel.org/r/alpine.DEB.2.22.394.2109081340540.668072@gentwo.de Signed-off-by: Christoph Lameter <cl@linux.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.