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iflib: netmap: fix rsync index overrun

Authored by vmaffione on Jun 13 2020, 7:50 AM.



In the current iflib_netmap_rxsync, there is nothing that prevents kring->nr_hwtail to overrun kring->nr_hwcur during the descriptor import phase. This may cause errors in netmap applications, such as:

em1 RX0: fail 'head < kring->nr_hwcur || head > kring->nr_hwtail' h 795 c 795 t 282 rh 795 rc 795 rt 282 hc 282 ht 282
Test Plan

Tested on an em device in a VM. After the patch, the problem disappears.

Diff Detail

rS FreeBSD src repository
Automatic diff as part of commit; lint not applicable.
Automatic diff as part of commit; unit tests not applicable.

Event Timeline

I guess no objections here? This is an easy change, that fixes a bug that is very easy to reproduce, and that prevents netmap applications from working for real on iflib.

This revision is now accepted and ready to land.Jun 23 2020, 3:00 PM
This revision was automatically updated to reflect the committed changes.