Author: royger
Date: Fri Jul  3 12:09:05 2015
New Revision: 285089
URL: https://svnweb.freebsd.org/changeset/base/285089

Log:
  netfront: preserve configuration across migrations
  
  Try to preserve the xn configuration when migrating. This is not always
  possible since the backend might not have the same set of options
  available, in which case we will try to preserve as many as possible.
  
  MFC after:    2 weeks
  PR:           183139
  Reported by:  [email protected]
  Sponsored by: Citrix Systems R&D

Modified:
  head/sys/dev/xen/netfront/netfront.c

Modified: head/sys/dev/xen/netfront/netfront.c
==============================================================================
--- head/sys/dev/xen/netfront/netfront.c        Fri Jul  3 11:16:20 2015        
(r285088)
+++ head/sys/dev/xen/netfront/netfront.c        Fri Jul  3 12:09:05 2015        
(r285089)
@@ -285,6 +285,8 @@ struct netfront_info {
        multicall_entry_t       rx_mcl[NET_RX_RING_SIZE+1];
        mmu_update_t            rx_mmu[NET_RX_RING_SIZE];
        struct ifmedia          sc_media;
+
+       bool                    xn_resume;
 };
 
 #define rx_mbufs xn_cdata.xn_rx_chain
@@ -500,6 +502,7 @@ netfront_resume(device_t dev)
 {
        struct netfront_info *info = device_get_softc(dev);
 
+       info->xn_resume = true;
        netif_disconnect_backend(info);
        return (0);
 }
@@ -1982,18 +1985,33 @@ xn_query_features(struct netfront_info *
 static int
 xn_configure_features(struct netfront_info *np)
 {
-       int err;
+       int err, cap_enabled;
 
        err = 0;
+
+       if (np->xn_resume &&
+           ((np->xn_ifp->if_capenable & np->xn_ifp->if_capabilities)
+           == np->xn_ifp->if_capenable)) {
+               /* Current options are available, no need to do anything. */
+               return (0);
+       }
+
+       /* Try to preserve as many options as possible. */
+       if (np->xn_resume)
+               cap_enabled = np->xn_ifp->if_capenable;
+       else
+               cap_enabled = UINT_MAX;
+
 #if __FreeBSD_version >= 700000 && (defined(INET) || defined(INET6))
-       if ((np->xn_ifp->if_capenable & IFCAP_LRO) != 0)
+       if ((np->xn_ifp->if_capenable & IFCAP_LRO) == (cap_enabled & IFCAP_LRO))
                tcp_lro_free(&np->xn_lro);
 #endif
        np->xn_ifp->if_capenable =
-           np->xn_ifp->if_capabilities & ~(IFCAP_LRO|IFCAP_TSO4);
+           np->xn_ifp->if_capabilities & ~(IFCAP_LRO|IFCAP_TSO4) & cap_enabled;
        np->xn_ifp->if_hwassist &= ~CSUM_TSO;
 #if __FreeBSD_version >= 700000 && (defined(INET) || defined(INET6))
-       if (xn_enable_lro && (np->xn_ifp->if_capabilities & IFCAP_LRO) != 0) {
+       if (xn_enable_lro && (np->xn_ifp->if_capabilities & IFCAP_LRO) ==
+           (cap_enabled & IFCAP_LRO)) {
                err = tcp_lro_init(&np->xn_lro);
                if (err) {
                        device_printf(np->xbdev, "LRO initialization failed\n");
@@ -2002,7 +2020,8 @@ xn_configure_features(struct netfront_in
                        np->xn_ifp->if_capenable |= IFCAP_LRO;
                }
        }
-       if ((np->xn_ifp->if_capabilities & IFCAP_TSO4) != 0) {
+       if ((np->xn_ifp->if_capabilities & IFCAP_TSO4) ==
+           (cap_enabled & IFCAP_TSO4)) {
                np->xn_ifp->if_capenable |= IFCAP_TSO4;
                np->xn_ifp->if_hwassist |= CSUM_TSO;
        }
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