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Date:      Tue, 7 Apr 2015 19:46:19 +0000 (UTC)
From:      Gleb Smirnoff <glebius@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-projects@freebsd.org
Subject:   svn commit: r281227 - in projects/ifnet/sys: dev/cxgbe net netgraph
Message-ID:  <201504071946.t37JkJWt013767@svn.freebsd.org>
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Author: glebius
Date: Tue Apr  7 19:46:18 2015
New Revision: 281227
URL: https://svnweb.freebsd.org/changeset/base/281227

Log:
  For the sake of network stack backpressure indication, as well as for
  properly implementing ALTQ, change KPI for ifop_transmit(). Now the
  transmit method must not free an mbuf, when it returns an error, since
  the caller could have plans for the mbuf.
  
  Sponsored by:	Netflix
  Sponsored by:	Nginx, Inc.

Modified:
  projects/ifnet/sys/dev/cxgbe/t4_main.c
  projects/ifnet/sys/net/if.c
  projects/ifnet/sys/net/if_var.h
  projects/ifnet/sys/net/if_vlan.c
  projects/ifnet/sys/netgraph/ng_iface.c

Modified: projects/ifnet/sys/dev/cxgbe/t4_main.c
==============================================================================
--- projects/ifnet/sys/dev/cxgbe/t4_main.c	Tue Apr  7 19:39:23 2015	(r281226)
+++ projects/ifnet/sys/dev/cxgbe/t4_main.c	Tue Apr  7 19:46:18 2015	(r281227)
@@ -1363,10 +1363,8 @@ cxgbe_transmit(if_t ifp, struct mbuf *m)
 	M_ASSERTPKTHDR(m);
 	MPASS(m->m_nextpkt == NULL);	/* not quite ready for this yet */
 
-	if (__predict_false(pi->link_cfg.link_ok == 0)) {
-		m_freem(m);
+	if (__predict_false(pi->link_cfg.link_ok == 0))
 		return (ENETDOWN);
-	}
 
 	rc = parse_pkt(&m);
 	if (__predict_false(rc != 0)) {
@@ -1383,8 +1381,6 @@ cxgbe_transmit(if_t ifp, struct mbuf *m)
 
 	items[0] = m;
 	rc = mp_ring_enqueue(txq->r, items, 1, 4096);
-	if (__predict_false(rc != 0))
-		m_freem(m);
 
 	return (rc);
 }

Modified: projects/ifnet/sys/net/if.c
==============================================================================
--- projects/ifnet/sys/net/if.c	Tue Apr  7 19:39:23 2015	(r281226)
+++ projects/ifnet/sys/net/if.c	Tue Apr  7 19:46:18 2015	(r281227)
@@ -3747,10 +3747,8 @@ if_snd_enqueue(struct ifnet *ifp, struct
 	mtx_lock(&ifq->ifq_mtx);
 	error = mbufq_enqueue(&ifq->ifq_mbq, m);
 	mtx_unlock(&ifq->ifq_mtx);
-	if (error) {
-		m_freem(m);
+	if (error)
 		if_inc_counter(ifp, IFCOUNTER_OQDROPS, 1);
-	}
 	return (error);
 }
 

Modified: projects/ifnet/sys/net/if_var.h
==============================================================================
--- projects/ifnet/sys/net/if_var.h	Tue Apr  7 19:39:23 2015	(r281226)
+++ projects/ifnet/sys/net/if_var.h	Tue Apr  7 19:46:18 2015	(r281227)
@@ -460,8 +460,12 @@ if_input(if_t ifp, struct mbuf *m)
 static inline int
 if_transmit(if_t ifp, struct mbuf *m)
 {
+	int error;
 
-	return (ifp->if_ops->ifop_transmit(ifp, m));
+	error = ifp->if_ops->ifop_transmit(ifp, m);
+	if (error)
+		m_freem(m);
+	return (error);
 }
 
 static inline void

Modified: projects/ifnet/sys/net/if_vlan.c
==============================================================================
--- projects/ifnet/sys/net/if_vlan.c	Tue Apr  7 19:39:23 2015	(r281226)
+++ projects/ifnet/sys/net/if_vlan.c	Tue Apr  7 19:46:18 2015	(r281227)
@@ -1012,7 +1012,6 @@ vlan_transmit(struct ifnet *ifp, struct 
 	 * Do not run parent's if_transmit() if the parent is not up.
 	 */
 	if (!(p->if_flags & IFF_UP)) {
-		m_freem(m);
 		if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
 		return (ENETDOWN);
 	}

Modified: projects/ifnet/sys/netgraph/ng_iface.c
==============================================================================
--- projects/ifnet/sys/netgraph/ng_iface.c	Tue Apr  7 19:39:23 2015	(r281226)
+++ projects/ifnet/sys/netgraph/ng_iface.c	Tue Apr  7 19:46:18 2015	(r281227)
@@ -398,7 +398,6 @@ ng_iface_send(if_t ifp, struct mbuf *m, 
 
 	/* Check address family to determine hook (if known) */
 	if (iffam == NULL) {
-		m_freem(m);
 		log(LOG_WARNING, "%s: can't handle af%d\n", if_name(ifp), sa);
 		return (EAFNOSUPPORT);
 	}
@@ -418,7 +417,8 @@ ng_iface_send(if_t ifp, struct mbuf *m, 
 	} else
 		if_inc_counter(ifp, IFCOUNTER_OERRORS, 1);
 
-	return (error);
+	/* Netgraph frees the mbuf, so we can't return an error. */
+	return (0);
 }
 
 #ifdef DEBUG

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