Improvements to netlink event parsing.

1. Accept that parseNetlinkMessage can only parse one netlink
   message, because its way of returning output is to modify its
   member variables (mAction, mParams, etc.). Currently, it
   loops through all the messages it finds, updating its member
   variables as it goes along, and always returns true at the end
   of the buffer. This has the following problems:

   1. Since the function always returns true even when no
      messages were parsed, the caller has no way to know if
      parsing succeeded, and we get lots of "No subsystem found
      in netlink event" logs if the buffer did not contain any
      valid messages we were interested in.
   2. If there are multiple messages in the buffer, all but the
      last message will be silently ignored.
   3. If there are multiple messages and previous messages have
      more parameters than the last one, the resulting event will
      have a mixture of parameters from multiple messages.

   Instead of doing all this, change the contract to "parse the
   first valid message of interest in the buffer and return true,
   or return false if there were no such messages", and update
   the code and the comments accordingly.

2. Modify the caller (NetlinkListener) so it doesn't log an
   error when parseBinaryNetlinkMessage returns false, because
   this can now simply mean that we weren't interested in that
   particular message. parseBinaryNetlinkMessage already logs
   more informative errors.

3. Provide utility functions to check received message lengths and
   to convert message types to message names.

4. Simplify logging duplicate attributes.

5. Use the appropriate IFLA_xxx macros instead of rolling our own
   code to parse link state messages.

6. Move all the parsing code out to per-message-type parsing
   functions to order to simplify parseBinaryNetlinkMessage.

Bug: 9180552
Change-Id: I6bbc2f7a104f618674dde2369c1fd5e93ea49430

1 files changed, 4 insertions, 2 deletions

diff --git a/include/sysutils/NetlinkEvent.h b/include/sysutils/NetlinkEvent.h
index c0a9418..a247a74 100644
--- a/include/sysutils/NetlinkEvent.h
+++ b/include/sysutils/NetlinkEvent.h
@@ -52,8 +52,10 @@ public:
  protected:
     bool parseBinaryNetlinkMessage(char *buffer, int size);
     bool parseAsciiNetlinkMessage(char *buffer, int size);
-    bool parseIfAddrMessage(int type, struct ifaddrmsg *ifaddr, int rtasize);
-    bool parseNdUserOptMessage(struct nduseroptmsg *msg, int optsize);
+    bool parseIfInfoMessage(const struct nlmsghdr *nh);
+    bool parseIfAddrMessage(const struct nlmsghdr *nh);
+    bool parseUlogPacketMessage(const struct nlmsghdr *nh);
+    bool parseNdUserOptMessage(const struct nlmsghdr *nh);
 };
 
 #endif