The easiest way of knowing when you are dealing with a structure, is when the code is calling functions for which you know (or documentation states) takes a structure as an argument.

For example the in_addr structure of the inet_ntoa function.

The easiest way of knowing when you are dealing with a structure, is when the code is calling functions for which you know (or documentation states) takes a structure as an argument.

For example the in_addr structure of the inet_ntoa function.

Given that IDA didn't figure this out in the first place.