[src/trunk]: src/sys/dev/ic Do not unilaterally set M_HASFCS; this breaks pro...

[sekiya <sekiya%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/ab147bf0b8b2
branches:  trunk
changeset: 368795:ab147bf0b8b2
user:      sekiya <sekiya%NetBSD.org@localhost>
date:      Fri Aug 05 21:03:43 2022 +0000

description:
Do not unilaterally set M_HASFCS; this breaks protocols that lack CRC bytes
(such as AppleTalk).

Instead, remove/preserve the final four bytes in the packet ourselves on a per-
protocol basis, as we do in arch/arm/xscale/ixp425_if_npe.c (and dev/ic/gem.c,
and so forth).

diffstat:

 sys/dev/ic/dwc_gmac.c |  29 ++++++++++++++++++++++++++---
 1 files changed, 26 insertions(+), 3 deletions(-)

diffs (58 lines):

diff -r 55ebe3c5a8af -r ab147bf0b8b2 sys/dev/ic/dwc_gmac.c
--- a/sys/dev/ic/dwc_gmac.c     Fri Aug 05 20:59:54 2022 +0000
+++ b/sys/dev/ic/dwc_gmac.c     Fri Aug 05 21:03:43 2022 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: dwc_gmac.c,v 1.75 2021/09/11 20:28:06 andvar Exp $ */
+/* $NetBSD: dwc_gmac.c,v 1.76 2022/08/05 21:03:43 sekiya Exp $ */
 
 /*-
  * Copyright (c) 2013, 2014 The NetBSD Foundation, Inc.
@@ -41,7 +41,7 @@
 
 #include <sys/cdefs.h>
 
-__KERNEL_RCSID(1, "$NetBSD: dwc_gmac.c,v 1.75 2021/09/11 20:28:06 andvar Exp $");
+__KERNEL_RCSID(1, "$NetBSD: dwc_gmac.c,v 1.76 2022/08/05 21:03:43 sekiya Exp $");
 
 /* #define     DWC_GMAC_DEBUG  1 */
 
@@ -1229,6 +1229,8 @@
        struct mbuf *m, *mnew;
        int i, len, error;
 
+       uint16_t etype;
+
        mutex_enter(&sc->sc_rxq.r_mtx);
        for (i = sc->sc_rxq.r_cur; ; i = RX_NEXT(i)) {
                bus_dmamap_sync(sc->sc_dmat, sc->sc_dma_ring_map,
@@ -1311,8 +1313,29 @@
                /* finalize mbuf */
                m->m_pkthdr.len = m->m_len = len;
                m_set_rcvif(m, ifp);
-               m->m_flags |= M_HASFCS;
+
+#define ETYPE_OFFSET 20
+               etype = (m->m_data[ETYPE_OFFSET] << 8) + m->m_data[ETYPE_OFFSET+1];
+
+               /*
+                * The hardware doesn't trim the four FCS bytes for us, so
+                * we need to trim it ourselves.
+                * Having the upper layer remove it by passing M_HASFCS breaks
+                * protocols that don't have FCS bytes at the end of the packet
+                * (AppleTalk, for example), so we do it here instead.
+                */
 
+               switch (etype) {
+                       case ETHERTYPE_ATALK:
+                       case ETHERTYPE_AARP:
+                               /* No FCS removal needed */
+                               break;
+                       default:
+                               /* remove FCS */
+                               m_adj(m, -ETHER_CRC_LEN);
+                               break;
+               }
+       
                if_percpuq_enqueue(sc->sc_ipq, m);
 
 skip: