[stp] Add support for detecting Spanning Tree Protocol non-forwarding ports

A fairly common end-user problem is that the default configuration of
a switch may leave the port in a non-forwarding state for a
substantial length of time (tens of seconds) after link up.  This can
cause iPXE to time out and give up attempting to boot.

We cannot force the switch to start forwarding packets sooner, since
any attempt to send a Spanning Tree Protocol bridge PDU may cause the
switch to disable our port (if the switch happens to have the Bridge
PDU Guard feature enabled for the port).

For non-ancient versions of the Spanning Tree Protocol, we can detect
whether or not the port is currently forwarding and use this to inform
the network device core that the link is currently blocked.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 152 insertions, 0 deletions

diff --git a/src/net/stp.c b/src/net/stp.c
new file mode 100644
index 00000000..cafb6b8e
--- /dev/null
+++ b/src/net/stp.c
@@ -0,0 +1,152 @@
+/*
+ * Copyright (C) 2015 Michael Brown <mbrown@fensystems.co.uk>.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <errno.h>
+#include <byteswap.h>
+#include <ipxe/netdevice.h>
+#include <ipxe/ethernet.h>
+#include <ipxe/iobuf.h>
+#include <ipxe/timer.h>
+#include <ipxe/stp.h>
+
+/** @file
+ *
+ * Spanning Tree Protocol (STP)
+ *
+ */
+
+/* Disambiguate the various error causes */
+#define ENOTSUP_PROTOCOL __einfo_error ( EINFO_ENOTSUP_PROTOCOL )
+#define EINFO_ENOTSUP_PROTOCOL					\
+	__einfo_uniqify ( EINFO_ENOTSUP, 0x01,			\
+			  "Non-STP packet received" )
+#define ENOTSUP_VERSION __einfo_error ( EINFO_ENOTSUP_VERSION )
+#define EINFO_ENOTSUP_VERSION					\
+	__einfo_uniqify ( EINFO_ENOTSUP, 0x01,			\
+			  "Legacy STP packet received" )
+#define ENOTSUP_TYPE __einfo_error ( EINFO_ENOTSUP_TYPE )
+#define EINFO_ENOTSUP_TYPE					\
+	__einfo_uniqify ( EINFO_ENOTSUP, 0x01,			\
+			  "Non-RSTP packet received" )
+
+/**
+ * Process incoming STP packets
+ *
+ * @v iobuf		I/O buffer
+ * @v netdev		Network device
+ * @v ll_source		Link-layer source address
+ * @v flags		Packet flags
+ * @ret rc		Return status code
+ */
+static int stp_rx ( struct io_buffer *iobuf, struct net_device *netdev,
+		    const void *ll_dest __unused,
+		    const void *ll_source __unused,
+		    unsigned int flags __unused ) {
+	struct stp_bpdu *stp;
+	unsigned int timeout;
+	int rc;
+
+	/* Sanity check */
+	if ( iob_len ( iobuf ) < sizeof ( *stp ) ) {
+		DBGC ( netdev, "STP %s received underlength packet (%zd "
+		       "bytes):\n", netdev->name, iob_len ( iobuf ) );
+		DBGC_HDA ( netdev, 0, iobuf->data, iob_len ( iobuf ) );
+		rc = -EINVAL;
+		goto done;
+	}
+	stp = iobuf->data;
+
+	/* Ignore non-RSTP packets */
+	if ( stp->protocol != htons ( STP_PROTOCOL ) ) {
+		DBGC ( netdev, "STP %s ignoring non-STP packet (protocol "
+		       "%#04x)\n", netdev->name, ntohs ( stp->protocol ) );
+		rc = -ENOTSUP_PROTOCOL;
+		goto done;
+	}
+	if ( stp->version < STP_VERSION_RSTP ) {
+		DBGC ( netdev, "STP %s received legacy STP packet (version "
+		       "%#02x)\n", netdev->name, stp->version );
+		rc = -ENOTSUP_VERSION;
+		goto done;
+	}
+	if ( stp->type != STP_TYPE_RSTP ) {
+		DBGC ( netdev, "STP %s received non-RSTP packet (type %#02x)\n",
+		       netdev->name, stp->type );
+		rc = -ENOTSUP_TYPE;
+		goto done;
+	}
+
+	/* Dump information */
+	DBGC2 ( netdev, "STP %s %s port %#04x flags %#02x hello %d delay %d\n",
+		netdev->name, eth_ntoa ( stp->sender.mac ), ntohs ( stp->port ),
+		stp->flags, ntohs ( stp->hello ), ntohs ( stp->delay ) );
+
+	/* Check if port is forwarding */
+	if ( ! ( stp->flags & STP_FL_FORWARDING ) ) {
+		/* Port is not forwarding: block link for two hello times */
+		DBGC ( netdev, "STP %s %s port %#04x flags %#02x is not "
+		       "forwarding\n",
+		       netdev->name, eth_ntoa ( stp->sender.mac ),
+		       ntohs ( stp->port ), stp->flags );
+		timeout = ( ntohs ( stp->hello ) * TICKS_PER_SEC * 2 );
+		netdev_link_block ( netdev, timeout );
+		rc = -ENETUNREACH;
+		goto done;
+	}
+
+	/* Success */
+	if ( netdev_link_blocked ( netdev ) ) {
+		DBGC ( netdev, "STP %s %s port %#04x flags %#02x is "
+		       "forwarding\n",
+		       netdev->name, eth_ntoa ( stp->sender.mac ),
+		       ntohs ( stp->port ), stp->flags );
+	}
+	netdev_link_unblock ( netdev );
+	rc = 0;
+
+ done:
+	free_iob ( iobuf );
+	return rc;
+}
+
+/**
+ * Transcribe STP address
+ *
+ * @v net_addr		STP address
+ * @ret string		"<STP>"
+ *
+ * This operation is meaningless for the STP protocol.
+ */
+static const char * stp_ntoa ( const void *net_addr __unused ) {
+	return "<STP>";
+}
+
+/** STP network protocol */
+struct net_protocol stp_protocol __net_protocol = {
+	.name = "STP",
+	.net_proto = htons ( ETH_P_STP ),
+	.rx = stp_rx,
+	.ntoa = stp_ntoa,
+};