UDP -sV speedup ideas

[dmiller-nmap]

UDP scanning is one of the slowest processes for Nmap, due largely to the fact that most invalid UDP datagrams are ignored by the target service. nmap-payloads remedies this somewhat by defining data payloads that have a high chance of eliciting a response from a target service on a particular port. We also have probes defined in nmap-service-probes that are designed to get a unique response from various software implementations. If we used these probes as data payloads, we could increase the chance of getting a response from various UDP services. Other benefits might result as well.

Brief description of work items necessary to accomplish this:

• Extend functions from payload.cc to retrieve payloads from the AllProbes class defined in service_scan.h
• Ensure "duplicate payload" warnings are not produced at normal or verbosity level 1 when they come from this retrieval.

A good solution will also:

• avoid duplicating payload data in memory, perhaps by linking the struct payload to the ServiceProbe it is related to.

Ideally, we would like to:

• Save any responses to probes from the port scan phase in order to match them in the service scan phase.
• Save any responses to payloads from the port scan phase in order to print them in the service fingerprint if the service scan does not find a match.
• Provide a means such as a nmap-service-probes directive to avoid sending a probe in this manner, for the case where a particular probe is found to be unsuitable for this