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SubjectRE: [PATCH] Infiniband: Randomize local port allocation.
Date
>[PATCH] Infiniband: Randomize local port allocation.
>
>Randomize local port allocation in a way sctp_get_port_local() does.
>
>Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>

Thanks for fixing this long outstanding issue. :) The latest patch looks
correct and passed some simple tests that I ran against it. One comment below,
which I didn't catch before:

>---
> drivers/infiniband/core/cma.c | 69 ++++++++++++++---------------------------
>-
> 1 file changed, 24 insertions(+), 45 deletions(-)
>
>--- linux-2.6.34-rc4.orig/drivers/infiniband/core/cma.c
>+++ linux-2.6.34-rc4/drivers/infiniband/core/cma.c
>@@ -79,7 +79,6 @@ static DEFINE_IDR(sdp_ps);
> static DEFINE_IDR(tcp_ps);
> static DEFINE_IDR(udp_ps);
> static DEFINE_IDR(ipoib_ps);
>-static int next_port;
>
> struct cma_device {
> struct list_head list;
>@@ -1970,47 +1969,32 @@ err1:
>
> static int cma_alloc_any_port(struct idr *ps, struct rdma_id_private *id_priv)
> {
>- struct rdma_bind_list *bind_list;
>- int port, ret, low, high;
>-
>- bind_list = kzalloc(sizeof *bind_list, GFP_KERNEL);
>- if (!bind_list)
>- return -ENOMEM;
>-
>-retry:
>- /* FIXME: add proper port randomization per like inet_csk_get_port */
>- do {
>- ret = idr_get_new_above(ps, bind_list, next_port, &port);
>- } while ((ret == -EAGAIN) && idr_pre_get(ps, GFP_KERNEL));
>-
>- if (ret)
>- goto err1;
>+ static unsigned int last_used_port;
>+ int low, high, remaining;
>+ unsigned int rover;
>
> inet_get_local_port_range(&low, &high);
>- if (port > high) {
>- if (next_port != low) {
>- idr_remove(ps, port);
>- next_port = low;
>- goto retry;
>+ remaining = (high - low) + 1;
>+ rover = net_random() % remaining + low;
>+ do {
>+ rover++;
>+ if ((rover < low) || (rover > high))
>+ rover = low;

Assuming that we're likely to pick a valid port on the first try, it would be
more efficient to move the above 3 lines to the end of the while loop.

>+ if (last_used_port != rover &&
>+ !idr_find(ps, (unsigned short) rover)) {
>+ int ret = cma_alloc_port(ps, id_priv, rover);
>+ /*
>+ * Remember previously used port number in order to
>+ * avoid re-using same port immediately after it is
>+ * closed.
>+ */
>+ if (!ret)
>+ last_used_port = rover;
>+ if (ret != -EADDRNOTAVAIL)
>+ return ret;
> }
>- ret = -EADDRNOTAVAIL;
>- goto err2;
>- }
>-
>- if (port == high)
>- next_port = low;
>- else
>- next_port = port + 1;
>-
>- bind_list->ps = ps;
>- bind_list->port = (unsigned short) port;
>- cma_bind_port(bind_list, id_priv);
>- return 0;
>-err2:
>- idr_remove(ps, port);
>-err1:
>- kfree(bind_list);
>- return ret;
>+ } while (--remaining > 0);
>+ return -EADDRNOTAVAIL;
> }




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