revert revision 1.131, the code in question was later found to not ensure

the proper alignment requirement for the VLAN layer on strict alignment
architectures. This would result in Jumbo's working fine as long as VLANs
were not in use. If VLANs were in use and a packet comes in with a size
of 2046 bytes or larger, it would be corrupted as it came up through the
VLAN layer. Also check the hw max frame size, instead of the MTU, so the
alignment fixup is done as appropriate.

Fixes PR 5185.
Tested by Rui DeSousa with macppc and myself with alpha/sparc64.

2 files changed, 57 insertions, 52 deletions

diff --git a/sys/dev/pci/if_em.c b/sys/dev/pci/if_em.c
index de11d01a114..d029794e30d 100644
--- a/sys/dev/pci/if_em.c
+++ b/sys/dev/pci/if_em.c
@@ -31,7 +31,7 @@ POSSIBILITY OF SUCH DAMAGE.
 
 ***************************************************************************/
 
-/* $OpenBSD: if_em.c,v 1.146 2006/08/22 15:51:18 brad Exp $ */
+/* $OpenBSD: if_em.c,v 1.147 2006/09/17 17:51:01 brad Exp $ */
 /* $FreeBSD: if_em.c,v 1.46 2004/09/29 18:28:28 mlaier Exp $ */
 
 #include <dev/pci/if_em.h>
@@ -151,9 +151,6 @@ void em_txeof(struct em_softc *);
 int  em_allocate_receive_structures(struct em_softc *);
 int  em_allocate_transmit_structures(struct em_softc *);
 void em_rxeof(struct em_softc *, int);
-#ifdef __STRICT_ALIGNMENT
-void em_fixup_rx(struct em_softc *);
-#endif
 void em_receive_checksum(struct em_softc *, struct em_rx_desc *,
 			 struct mbuf *);
 void em_transmit_checksum_setup(struct em_softc *, struct mbuf *,
@@ -2435,6 +2432,55 @@ em_rxeof(struct em_softc *sc, int count)
 			/* Assign correct length to the current fragment */
 			mp->m_len = len;
 
+#ifdef __STRICT_ALIGNMENT
+			/*
+			 * The Ethernet payload is not 32-bit aligned when
+			 * Jumbo packets are enabled, so on architectures with
+			 * strict alignment we need to shift the entire packet
+			 * ETHER_ALIGN bytes. Ugh.
+			 */
+			if (sc->hw.max_frame_size > (MCLBYTES - ETHER_ALIGN)) {
+				unsigned char tmp_align_buf[ETHER_ALIGN];
+				int tmp_align_buf_len = 0;
+
+				if (prev_len_adj > sc->align_buf_len)
+					prev_len_adj -= sc->align_buf_len;
+				else
+					prev_len_adj = 0;
+
+				if (mp->m_len > (MCLBYTES - ETHER_ALIGN)) {
+					bcopy(mp->m_data +
+					    (MCLBYTES - ETHER_ALIGN),
+					    &tmp_align_buf,
+					    ETHER_ALIGN);
+					tmp_align_buf_len = mp->m_len -
+					    (MCLBYTES - ETHER_ALIGN);
+					mp->m_len -= ETHER_ALIGN;
+				} 
+
+				if (mp->m_len) {
+					bcopy(mp->m_data,
+					    mp->m_data + ETHER_ALIGN,
+					    mp->m_len);
+					if (!sc->align_buf_len)
+						mp->m_data += ETHER_ALIGN;
+				}
+
+				if (sc->align_buf_len) {
+					mp->m_len += sc->align_buf_len;
+					bcopy(&sc->align_buf,
+					    mp->m_data,
+					    sc->align_buf_len);
+				}
+
+				if (tmp_align_buf_len) 
+					bcopy(&tmp_align_buf,
+					    &sc->align_buf,
+					    tmp_align_buf_len);
+				sc->align_buf_len = tmp_align_buf_len;
+			}
+#endif /* __STRICT_ALIGNMENT */
+
 			if (sc->fmp == NULL) {
 				mp->m_pkthdr.len = mp->m_len;
 				sc->fmp = mp;	 /* Store the first mbuf */
@@ -2460,10 +2506,6 @@ em_rxeof(struct em_softc *sc, int count)
 				ifp->if_ipackets++;
 				em_receive_checksum(sc, current_desc,
 					    sc->fmp);
-#ifdef __STRICT_ALIGNMENT
-				if (sc->hw.max_frame_size > (MCLBYTES - ETHER_ALIGN))
-					em_fixup_rx(sc);
-#endif
 				m = sc->fmp;
 				sc->fmp = NULL;
 				sc->lmp = NULL;
@@ -2512,49 +2554,6 @@ em_rxeof(struct em_softc *sc, int count)
 	E1000_WRITE_REG(&sc->hw, RDT, i);
 }
 
-#ifdef __STRICT_ALIGNMENT
-/*
- * When Jumbo frames are enabled we should realign the entire payload on
- * strict alignment architecures. This is a serious design mistake of the
- * 8254x chipset as it nullifies DMA operations. 8254x allows the RX buffer
- * size to be 2048/4096/8192/16384. What we really want is 2048 - ETHER_ALIGN
- * to align its payload. On non strict alignment architectures 8254x still
- * performs unaligned memory access which will reduce the performance too. To
- * avoid copying over an entire frame to align, we allocate a new mbuf and
- * copy the Ethernet header to the new mbuf. The new mbuf is then prepended
- * into the existing mbuf chain.
- *
- * Be aware, best performance of the 8254x chipset is achived only when Jumbo
- * frames are not used at all on strict alignment architectures.
- */
-void
-em_fixup_rx(struct em_softc *sc)
-{
-	struct mbuf *m, *n;
-
-	m = sc->fmp;
-	if (m->m_len <= (MCLBYTES - ETHER_HDR_LEN)) {
-		bcopy(m->m_data, m->m_data + ETHER_HDR_LEN, m->m_len);
-		m->m_data += ETHER_HDR_LEN;
-	} else {
-		MGETHDR(n, M_DONTWAIT, MT_DATA);
-		if (n != NULL) {
-			bcopy(m->m_data, n->m_data, ETHER_HDR_LEN);
-			m->m_data += ETHER_HDR_LEN;
-			m->m_len -= ETHER_HDR_LEN;
-			n->m_len = ETHER_HDR_LEN;
-			M_MOVE_PKTHDR(n, m);
-			n->m_next = m;
-			sc->fmp = n;
-		} else {
-			sc->dropped_pkts++;
-			m_freem(sc->fmp);
-			sc->fmp = NULL;
-		}
-	}
-}
-#endif
-
 /*********************************************************************
  *
  *  Verify that the hardware indicated that the checksum is valid. 
diff --git a/sys/dev/pci/if_em.h b/sys/dev/pci/if_em.h
index de249735763..8a7f970cbb3 100644
--- a/sys/dev/pci/if_em.h
+++ b/sys/dev/pci/if_em.h
@@ -32,7 +32,7 @@ POSSIBILITY OF SUCH DAMAGE.
 ***************************************************************************/
 
 /* $FreeBSD: if_em.h,v 1.26 2004/09/01 23:22:41 pdeuskar Exp $ */
-/* $OpenBSD: if_em.h,v 1.27 2006/08/04 14:25:24 brad Exp $ */
+/* $OpenBSD: if_em.h,v 1.28 2006/09/17 17:51:01 brad Exp $ */
 
 #ifndef _EM_H_DEFINED_
 #define _EM_H_DEFINED_
@@ -310,6 +310,12 @@ struct em_softc {
 	void		*sc_powerhook;
 	void		*sc_shutdownhook;
 
+#ifdef __STRICT_ALIGNMENT
+	/* Used for carrying forward alignment adjustments */
+	unsigned char	align_buf[ETHER_ALIGN];	/* tail of unaligned packet */
+	u_int8_t	align_buf_len;		/* bytes in tail */
+#endif /* __STRICT_ALIGNMENT */
+
 	/* Info about the board itself */
 	u_int32_t	part_num;
 	u_int8_t	link_active;