Re: 5.15-rc3+ crash in fq-codel?

On 9/29/21 5:04 PM, Ben Greear wrote:

On 9/29/21 4:48 PM, Ben Greear wrote:

quoted

On 9/29/21 4:42 PM, Eric Dumazet wrote:

quoted

On 9/29/21 4:28 PM, Eric Dumazet wrote:

quoted

quoted

Actually the bug seems to be in pktgen, vs NET_XMIT_CN

You probably would hit the same issues with other qdisc also using NET_XMIT_CN

I would try the following patch :

diff --git a/net/core/pktgen.c b/net/core/pktgen.c
index a3d74e2704c42e3bec1aa502b911c1b952a56cf1..0a2d9534f8d08d1da5dfc68c631f3a07f95c6f77 100644
--- a/net/core/pktgen.c
+++ b/net/core/pktgen.c

@@ -3567,6 +3567,7 @@ static void pktgen_xmit(struct pktgen_dev *pkt_dev)

         case NET_XMIT_DROP:
         case NET_XMIT_CN:
                 /* skb has been consumed */
+               pkt_dev->last_ok = 1;
                 pkt_dev->errors++;
                 break;
         default: /* Drivers are not supposed to return other values! */

While patching my variant of pktgen, I took a look at the 'default' case.  I think
it should probably go above NET_XMIT_DROP and fallthrough into the consumed pkt path?

Although, probably not a big deal since only bugs elsewhere would hit that path, and
we don't really know if skb would be consumed in that case or not.

This is probably dead code after commit

commit f466dba1832f05006cf6caa9be41fb98d11cb848    pktgen: ndo_start_xmit can return NET_XMIT_xxx values

So this does not really matter anymore.