netlink-socket: Always pass the output buffer in a transaction.

We need to pass down the output buffer so that the kernel can return
transaction status - error or otherwise.

Also, we were processing the output buffer only when when
'txn->reply != NULL' ie when the caller specified an ofpbuf for the
reply. In this patch, the code has been updated to process the reply
unconditionally, but making sure to copy the reply to the 'txn->reply'
only when it is not NULL. The reason for the unconditional processing is
we can pass up transactional errors in 'txn->error'. Otherwise, it
results in an endless loop of calling nl_transact().

Signed-off-by: Nithin Raju <nithin@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Ankur Sharma <ankursharma@vmware.com>

1 files changed, 37 insertions, 43 deletions

diff --git a/lib/netlink-socket.c b/lib/netlink-socket.c
index 1aa76aebf..7e30ab1dd 100644
--- a/lib/netlink-socket.c
+++ b/lib/netlink-socket.c
@@ -758,74 +758,68 @@ nl_sock_transact_multiple__(struct nl_sock *sock,
     ofpbuf_uninit(&tmp_reply);
 #else
     error = 0;
+    uint8_t reply_buf[65536];
     for (i = 0; i < n; i++) {
         DWORD reply_len;
-        uint8_t tail[65536];
         struct nl_transaction *txn = transactions[i];
         struct nlmsghdr *request_nlmsg, *reply_nlmsg;
 
         if (!DeviceIoControl(sock->handle, OVS_IOCTL_TRANSACT,
                              ofpbuf_data(txn->request),
                              ofpbuf_size(txn->request),
-                             txn->reply ? tail : 0,
-                             txn->reply ? sizeof tail : 0,
+                             reply_buf, sizeof reply_buf,
                              &reply_len, NULL)) {
             /* XXX: Map to a more appropriate error. */
             error = EINVAL;
             break;
         }
 
-        if (txn->reply) {
-            if (reply_len < sizeof *reply_nlmsg) {
-                VLOG_DBG_RL(&rl, "insufficient length of reply %#"PRIu32,
-                            reply_len);
-                break;
-            }
+        if (reply_len < sizeof *reply_nlmsg) {
+            nl_sock_record_errors__(transactions, n, 0);
+            VLOG_DBG_RL(&rl, "insufficient length of reply %#"PRIu32
+                " for seq: %#"PRIx32, reply_len, request_nlmsg->nlmsg_seq);
+            break;
+        }
 
-            /* Validate the sequence number in the reply. */
-            request_nlmsg = nl_msg_nlmsghdr(txn->request);
-            reply_nlmsg = (struct nlmsghdr *)tail;
+        /* Validate the sequence number in the reply. */
+        request_nlmsg = nl_msg_nlmsghdr(txn->request);
+        reply_nlmsg = (struct nlmsghdr *)reply_buf;
 
-            if (request_nlmsg->nlmsg_seq != reply_nlmsg->nlmsg_seq) {
-                ovs_assert(request_nlmsg->nlmsg_seq == reply_nlmsg->nlmsg_seq);
-                VLOG_DBG_RL(&rl, "mismatched seq request %#"PRIx32
-                    ", reply %#"PRIx32, request_nlmsg->nlmsg_seq,
-                    reply_nlmsg->nlmsg_seq);
-                break;
-            }
+        if (request_nlmsg->nlmsg_seq != reply_nlmsg->nlmsg_seq) {
+            ovs_assert(request_nlmsg->nlmsg_seq == reply_nlmsg->nlmsg_seq);
+            VLOG_DBG_RL(&rl, "mismatched seq request %#"PRIx32
+                ", reply %#"PRIx32, request_nlmsg->nlmsg_seq,
+                reply_nlmsg->nlmsg_seq);
+            break;
+        }
 
-            /* If reply was expected, verify if there was indeed a reply
-             * received. */
-            if (reply_len == 0) {
-                nl_sock_record_errors__(transactions, n, 0);
-                VLOG_DBG_RL(&rl, "reply not seen when expected seq %#"PRIx32,
-                            request_nlmsg->nlmsg_seq);
-                break;
+        /* Handle errors embedded within the netlink message. */
+        ofpbuf_use_stub(&tmp_reply, reply_buf, sizeof reply_buf);
+        ofpbuf_set_size(&tmp_reply, sizeof reply_buf);
+        if (nl_msg_nlmsgerr(&tmp_reply, &txn->error)) {
+            if (txn->reply) {
+                ofpbuf_clear(txn->reply);
             }
-
-            /* Copy the reply to the buffer specified by the caller. */
-            if (reply_len > txn->reply->allocated) {
-                ofpbuf_reinit(txn->reply, reply_len);
+            if (txn->error) {
+                VLOG_DBG_RL(&rl, "received NAK error=%d (%s)",
+                            error, ovs_strerror(txn->error));
             }
-            memcpy(ofpbuf_data(txn->reply), tail, reply_len);
-            ofpbuf_set_size(txn->reply, reply_len);
-
-            /* Handle errors embedded within the netlink message. */
-            if (nl_msg_nlmsgerr(txn->reply, &txn->error)) {
-                if (txn->reply) {
-                    ofpbuf_clear(txn->reply);
-                }
-                if (txn->error) {
-                    VLOG_DBG_RL(&rl, "received NAK error=%d (%s)",
-                                error, ovs_strerror(txn->error));
+        } else {
+            txn->error = 0;
+            if (txn->reply) {
+                /* Copy the reply to the buffer specified by the caller. */
+                if (reply_len > txn->reply->allocated) {
+                    ofpbuf_reinit(txn->reply, reply_len);
                 }
-            } else {
-                txn->error = 0;
+                memcpy(ofpbuf_data(txn->reply), reply_buf, reply_len);
+                ofpbuf_set_size(txn->reply, reply_len);
             }
         }
+        ofpbuf_uninit(&tmp_reply);
 
         /* Count the number of successful transactions. */
         (*done)++;
+
     }
 
     if (!error) {