On Fri, Feb 09, 2018 at 03:40:13PM +0100, Martin Pieuchot wrote: > On 02/02/18(Fri) 12:18, Michele Curti wrote: > > Hi, > > in sys/dev/pci/if_em.c at line 469 there is: > > sc->hw.min_frame_size = > > ETHER_MIN_LEN + ETHER_CRC_LEN; > > > > But ETHER_MIN_LEN already includes the CRC size: > > #define ETHER_MIN_LEN 64 /* Minimum frame length, CRC included */ > > > > In revision 1.41 the code changed in this way: > > sc->hw.min_frame_size = > > - MINIMUM_ETHERNET_PACKET_SIZE + ETHER_CRC_LEN; > > + ETHER_MIN_LEN + ETHER_CRC_LEN; > > > > But MINIMUM_ETHERNET_PACKET_SIZE was the size without CRC. > > > > #define MINIMUM_ETHERNET_FRAME_SIZE 64 /* With FCS */ > > #define ETHERNET_FCS_SIZE 4 > > #define MINIMUM_ETHERNET_PACKET_SIZE \ > > (MINIMUM_ETHERNET_FRAME_SIZE - ETHERNET_FCS_SIZE) > > > > So I attached the following diff to restore the original minimum > > size (by the way, what's the effect of having min_frame_size set > > to 68? Discarding valid packets sized from 64 to 67?) > > I agree with your analyse. How did you end up looking at this? Does > this fix a problem for you?
Hi Martin, no, I had no problems. I was reading "OpenBSD network stack internals" by Claudio Jeker, and I was just curious about it. So I started reading the code from the interrupt routine and had trouble with the byte count. The resolution led to this patch, but I haven't been able to understand if the patch may lead to regressions, despite the hints from other developers eheh... Regards, Michele > > > Index: sys/dev/pci/if_em.c > > =================================================================== > > RCS file: /cvs/src/sys/dev/pci/if_em.c,v > > retrieving revision 1.336 > > diff -u -p -r1.336 if_em.c > > --- sys/dev/pci/if_em.c 25 Jul 2017 20:45:18 -0000 1.336 > > +++ sys/dev/pci/if_em.c 2 Feb 2018 11:13:43 -0000 > > @@ -466,8 +466,7 @@ em_attach(struct device *parent, struct > > MAX_JUMBO_FRAME_SIZE; > > } > > > > - sc->hw.min_frame_size = > > - ETHER_MIN_LEN + ETHER_CRC_LEN; > > + sc->hw.min_frame_size = ETHER_MIN_LEN; > > > > /* Allocate Transmit Descriptor ring */ > > if (em_dma_malloc(sc, sc->sc_tx_slots * sizeof(struct em_tx_desc), > >