[ovs-dev] [PATCH] linux: Signal datapath that unaligned Netlink message can be received

[Thomas Graf]

Following commit (''netlink: Do not enforce alignment of last Netlink
attribute''), signal the ability to receive unaligned Netlink messages
to the datapath to enable utilization of zerocopy optimizations.

Signed-off-by: Thomas Graf <tg...@redhat.com>
---
 include/linux/openvswitch.h | 4 ++++
 lib/dpif-linux.c            | 6 ++++++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/openvswitch.h b/include/linux/openvswitch.h
index b429201..8b5726a 100644
--- a/include/linux/openvswitch.h
+++ b/include/linux/openvswitch.h
@@ -95,6 +95,7 @@ enum ovs_datapath_attr {
        OVS_DP_ATTR_UPCALL_PID,         /* Netlink PID to receive upcalls */
        OVS_DP_ATTR_STATS,              /* struct ovs_dp_stats */
        OVS_DP_ATTR_MEGAFLOW_STATS,     /* struct ovs_dp_megaflow_stats */
+       OVS_DP_ATTR_USER_FEATURES,      /* OVS_DP_F_*  */
        __OVS_DP_ATTR_MAX
 };
 
@@ -126,6 +127,9 @@ struct ovs_vport_stats {
        __u64   tx_dropped;             /* no space available in linux  */
 };
 
+/* Allow last Netlink attribute to be unaligned */
+#define OVS_DP_F_UNALIGNED (1 << 0)
+
 /* Fixed logical ports. */
 #define OVSP_LOCAL      ((__u32)0)
 
diff --git a/lib/dpif-linux.c b/lib/dpif-linux.c
index 42958d3..bc1395c 100644
--- a/lib/dpif-linux.c
+++ b/lib/dpif-linux.c
@@ -73,6 +73,7 @@ struct dpif_linux_dp {
     /* Attributes. */
     const char *name;                  /* OVS_DP_ATTR_NAME. */
     const uint32_t *upcall_pid;        /* OVS_DP_UPCALL_PID. */
+    uint32_t user_features;            /* OVS_DP_ATTR_USER_FEATURES */
     struct ovs_dp_stats stats;         /* OVS_DP_ATTR_STATS. */
     struct ovs_dp_megaflow_stats megaflow_stats;
                                        /* OVS_DP_ATTR_MEGAFLOW_STATS.*/
@@ -227,6 +228,7 @@ dpif_linux_open(const struct dpif_class *class OVS_UNUSED, 
const char *name,
     if (create) {
         dp_request.cmd = OVS_DP_CMD_NEW;
         upcall_pid = 0;
+        dp_request.user_features |= OVS_DP_F_UNALIGNED;
         dp_request.upcall_pid = &upcall_pid;
     } else {
         dp_request.cmd = OVS_DP_CMD_GET;
@@ -1839,6 +1841,10 @@ dpif_linux_dp_to_ofpbuf(const struct dpif_linux_dp *dp, 
struct ofpbuf *buf)
         nl_msg_put_u32(buf, OVS_DP_ATTR_UPCALL_PID, *dp->upcall_pid);
     }
 
+    if (dp->user_features) {
+        nl_msg_put_u32(buf, OVS_DP_ATTR_USER_FEATURES, dp->user_features);
+    }
+
     /* Skip OVS_DP_ATTR_STATS since we never have a reason to serialize it. */
 }
 
-- 
1.8.3.1

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