net: devmem: refresh devmem TX dst in case of route invalidation
[ Netdev upstream commit 6a2108c78069fda000729b88c97b1eba0405e6d7 ]
[ This needs an updated sha from upstream once the commit is merged]
The zero-copy Device Memory (Devmem) transmit path
relies on the socket's route cache (`dst_entry`) to
validate that the packet is being sent via the network
device to which the DMA buffer was bound.
However, this check incorrectly fails and returns `-ENODEV`
if the socket's route cache entry (`dst`) is merely missing
or expired (`dst == NULL`). This scenario is observed during
network events, such as when flow steering rules are deleted,
leading to a temporary route cache invalidation.
This patch fixes -ENODEV error for `net_devmem_get_binding()`
by doing the following:
1. It attempts to rebuild the route via `rebuild_header()`
if the route is initially missing (`dst == NULL`). This
allows the TCP/IP stack to recover from transient route
cache misses.
2. It uses `rcu_read_lock()` and `dst_dev_rcu()` to safely
access the network device pointer (`dst_dev`) from the
route, preventing use-after-free conditions if the
device is concurrently removed.
3. It maintains the critical safety check by validating
that the retrieved destination device (`dst_dev`) is
exactly the device registered in the Devmem binding
(`binding->dev`).
These changes prevent unnecessary ENODEV failures while
maintaining the critical safety requirement that the
Devmem resources are only used on the bound network device.
BUG=b/452457749
TEST=TcpxFunctionalTest
RELEASE_NOTE=Fixed a TCPX bug which would sometimes incorrectly report devices as being missing when route cache entries were missing or invalidated.
cos-patch: bug
Reviewed-by: Bobby Eshleman <bobbyeshleman@meta.com>
Reported-by: Eric Dumazet <edumazet@google.com>
Reported-by: Vedant Mathur <vedantmathur@google.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Fixes: bd61848900bf ("net: devmem: Implement TX path")
Change-Id: I14b2801731d7e24b224f50a3ee20379e58a4b350
Link: https://git.kernel.org/netdev/net/c/6a2108c78069
Signed-off-by: Shivaji Kant <shivajikant@google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/116381
Tested-by: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Main-Branch-Verified: Cusky Presubmit Bot <presubmit@cos-infra-prod.iam.gserviceaccount.com>
Reviewed-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Kevin Berry <kpberry@google.com>
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Reviewed-on: https://cos-review.googlesource.com/c/third_party/kernel/+/116701
1 file changed
