Always set the hardware parse bit in the IPCB structure when this

structure, which is new to the 82550 and 82551, is used to transmit
a packet.  This appears to fix the packet truncation problem that was
observed when using 82550-based fxp cards to transmit ICMP or fragmented
UDP packets of certain lengths which only had one to three bytes in the
second and final mbuf of the packet.  This matches a note in the "Intel
8255x 10/100 Mbps Ethernet Controller Family Open Source Software Developer
Manual", which says that the hardware parse bit should be set when sending
these types of packets.

There have also been unconfirmed reports of similar problems when
transmitting TCP packets, which should not be affected by the above
mentioned change because the hardware parse bit was already being set
if the stack requested hardware checksumming of the packet.  If the
problem remains, the use of the IPCB structure can be disabled to
cause the driver to fall back to using the older 82559 interface with
82550-based cards by setting
        hint.fxp.UNIT_NUMBER.ipcbxmit_disable
to a non-zero value at boot time, or using kenv to set this variable
before using kldload to load the fxp driver.

Approved by:	re (jhb)

1 files changed, 43 insertions, 6 deletions

diff --git a/sys/dev/fxp/if_fxp.c b/sys/dev/fxp/if_fxp.c
index 1124ede..881101d 100644
--- a/sys/dev/fxp/if_fxp.c
+++ b/sys/dev/fxp/if_fxp.c
@@ -383,7 +383,7 @@ fxp_attach(device_t dev)
 	u_int32_t val;
 	u_int16_t data, myea[ETHER_ADDR_LEN / 2];
 	int i, rid, m1, m2, prefer_iomap, maxtxseg;
-	int s;
+	int s, ipcbxmit_disable;
 
 	sc->dev = dev;
 	callout_handle_init(&sc->stat_ch);
@@ -582,9 +582,31 @@ fxp_attach(device_t dev)
 	 * and later chips. Note: we need extended TXCB support
 	 * too, but that's already enabled by the code above.
 	 * Be careful to do this only on the right devices.
-	 */
-
-	if (sc->revision == FXP_REV_82550 || sc->revision == FXP_REV_82550_C) {
+	 *
+	 * At least some 82550 cards probed as "chip=0x12298086 rev=0x0d"
+	 * truncate packets that end with an mbuf containing 1 to 3 bytes
+	 * when used with this feature enabled in the previous version of the
+	 * driver.  This problem appears to be fixed now that the driver
+	 * always sets the hardware parse bit in the IPCB structure, which
+	 * the "Intel 8255x 10/100 Mbps Ethernet Controller Family Open
+	 * Source Software Developer Manual" says is necessary in the
+	 * cases where packet truncation was observed.
+	 *
+	 * The device hint "hint.fxp.UNIT_NUMBER.ipcbxmit_disable"
+	 * allows this feature to be disabled at boot time.
+	 *
+	 * If fxp is not compiled into the kernel, this feature may also
+	 * be disabled at run time:
+	 *    # kldunload fxp
+	 *    # kenv hint.fxp.0.ipcbxmit_disable=1
+	 *    # kldload fxp
+	 */
+
+	if (resource_int_value("fxp", device_get_unit(dev), "ipcbxmit_disable",
+	    &ipcbxmit_disable) != 0)
+		ipcbxmit_disable = 0;
+	if (ipcbxmit_disable == 0 && (sc->revision == FXP_REV_82550 ||
+	    sc->revision == FXP_REV_82550_C)) {
 		sc->rfa_size = sizeof (struct fxp_rfa);
 		sc->tx_cmd = FXP_CB_COMMAND_IPCBXMIT;
 		sc->flags |= FXP_FLAG_EXT_RFA;
@@ -1277,6 +1299,23 @@ fxp_start_body(struct ifnet *ifp)
 		txp = sc->fxp_desc.tx_last->tx_next;
 
 		/*
+		 * A note in Appendix B of the Intel 8255x 10/100 Mbps
+		 * Ethernet Controller Family Open Source Software
+		 * Developer Manual says:
+		 *   Using software parsing is only allowed with legal
+		 *   TCP/IP or UDP/IP packets.
+		 *   ...
+		 *   For all other datagrams, hardware parsing must
+		 *   be used.
+		 * Software parsing appears to truncate ICMP and
+		 * fragmented UDP packets that contain one to three
+		 * bytes in the second (and final) mbuf of the packet.
+		 */
+		if (sc->flags & FXP_FLAG_EXT_RFA)
+			txp->tx_cb->ipcb_ip_activation_high =
+			    FXP_IPCB_HARDWAREPARSING_ENABLE;
+
+		/*
 		 * Deal with TCP/IP checksum offload. Note that
 		 * in order for TCP checksum offload to work,
 		 * the pseudo header checksum must have already
@@ -1287,8 +1326,6 @@ fxp_start_body(struct ifnet *ifp)
 
 		if (mb_head->m_pkthdr.csum_flags) {
 			if (mb_head->m_pkthdr.csum_flags & CSUM_DELAY_DATA) {
-				txp->tx_cb->ipcb_ip_activation_high =
-				    FXP_IPCB_HARDWAREPARSING_ENABLE;
 				txp->tx_cb->ipcb_ip_schedule =
 				    FXP_IPCB_TCPUDP_CHECKSUM_ENABLE;
 				if (mb_head->m_pkthdr.csum_flags & CSUM_TCP)