Does Confd provide any callback to intercept rpc attributes (eg: message-id or any custom attribute) sent via netconf rpc request?

Does Confd provide any callback to intercept rpc attributes (eg: message-id or any custom attribute) sent via netconf rpc request?

<?xml version="1.0" encoding="UTF-8"?>
<rpc xmlns="urn:ietf:params:xml:ns:netconf:base:1.0" message-id="1">
  <testrpc xmlns="http://example.com/ns/yang/testrpc"/>
</rpc>

Very limited. You can subscribe to CONFD_NOTIF_NETCONF events and your subscriber would get data structured according to

struct confd_syslog_notification {
    int prio;   /* from syslog.h */
    int logno;  /* number from confd_logsyms.h */
    char msg[BUFSIZ];
}

where some of what you ask for is in the message field. See the misc/notification example: do make START_FLAGS=-N all start, run NETCONF requests and watch the output to see if there is what you need.