netdev - [PATCH] pppoe: Use workqueue to die properly when a PADT is received

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Message-Id: <1424381068-22252-1-git-send-email-simon@farnz.org.uk>
Date:	Thu, 19 Feb 2015 21:24:28 +0000
From:	Simon Farnsworth <simon@...nz.org.uk>
To:	netdev@...r.kernel.org
Cc:	Michal Ostrowski <mostrows@...thlink.net>,
	Dan Williams <dcbw@...hat.com>,
	Simon Farnsworth <simon@...nz.org.uk>
Subject: [PATCH] pppoe: Use workqueue to die properly when a PADT is received

When a PADT frame is received, the socket may not be in a good state to
close down the PPP interface. The current implementation handles this by
simply blocking all further PPP traffic, and hoping that the lack of traffic
will trigger the user to investigate.

Use schedule_work to get to a process context from which we clear down the
PPP interface, in a fashion analogous to hangup on a TTY-based PPP
interface. This causes pppd to disconnect immediately, and allows tools to
take immediate corrective action.

Signed-off-by: Simon Farnsworth <simon@...nz.org.uk>
---
Note that I'm not subscribed to netdev; please cc me on any replies.

The patch falls out of https://bugzilla.gnome.org/show_bug.cgi?id=742939
I'm trying to get NetworkManager back to using kernel PPPoE partly because
it performs a little better, and mostly because kernel PPPoE copes with
larger MTUs than userspace PPPoE.

Dan Williams (cc'd) has tested a previous version of this patch; the
differences to this version are only cosmetic.

 drivers/net/ppp/pppoe.c  | 17 ++++++++++++++++-
 include/linux/if_pppox.h |  2 ++
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
index d2408a5..9c97e9b 100644
--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -455,6 +455,18 @@ out:
 	return NET_RX_DROP;
 }
 
+static void pppoe_unbind_sock_work(struct work_struct *work)
+{
+	struct pppox_sock *po = container_of(work, struct pppox_sock,
+					     proto.pppoe.padt_work);
+	struct sock *sk = sk_pppox(po);
+
+	lock_sock(sk);
+	pppox_unbind_sock(sk);
+	release_sock(sk);
+	sock_put(sk);
+}
+
 /************************************************************************
  *
  * Receive a PPPoE Discovery frame.
@@ -500,7 +512,8 @@ static int pppoe_disc_rcv(struct sk_buff *skb, struct net_device *dev,
 		}
 
 		bh_unlock_sock(sk);
-		sock_put(sk);
+		if (!schedule_work(&po->proto.pppoe.padt_work))
+			sock_put(sk);
 	}
 
 abort:
@@ -613,6 +626,8 @@ static int pppoe_connect(struct socket *sock, struct sockaddr *uservaddr,
 
 	lock_sock(sk);
 
+	INIT_WORK(&po->proto.pppoe.padt_work, pppoe_unbind_sock_work);
+
 	error = -EINVAL;
 	if (sp->sa_protocol != PX_PROTO_OE)
 		goto end;
diff --git a/include/linux/if_pppox.h b/include/linux/if_pppox.h
index aff7ad8..66a7d76 100644
--- a/include/linux/if_pppox.h
+++ b/include/linux/if_pppox.h
@@ -19,6 +19,7 @@
 #include <linux/netdevice.h>
 #include <linux/ppp_channel.h>
 #include <linux/skbuff.h>
+#include <linux/workqueue.h>
 #include <uapi/linux/if_pppox.h>
 
 static inline struct pppoe_hdr *pppoe_hdr(const struct sk_buff *skb)
@@ -32,6 +33,7 @@ struct pppoe_opt {
 	struct pppoe_addr	pa;	  /* what this socket is bound to*/
 	struct sockaddr_pppox	relay;	  /* what socket data will be
 					     relayed to (PPPoE relaying) */
+	struct work_struct      padt_work;/* Work item for handling PADT */
 };
 
 struct pptp_opt {
-- 
2.1.0

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