It does seem like search just ignores code blocks; I can't find any mention of if this is intentional, it seems like an odd decision, and the meta thread about the new search engine implies that it should work:

• Quoted phrases are exact matches except for case-sensitivity, for example, you can search for code or symbols.

There is a way to search only code blocks, the entirely undocumented code: filter, so code:"ip rule" is:a user:997 will work. Note that that wouldn't find answers where you mentioned "ip rule" outside a code block; I think you'd have to run two separate searches to cover both cases.

It does seem like search just ignores code blocks; I can't find any mention of if this is intentional, it seems like an odd decision, and the meta thread about the new search engine implies that it should work:

• Quoted phrases are exact matches except for case-sensitivity, for example, you can search for code or symbols.

There is a way to search only code blocks, the entirely undocumented code: filter, so code:"ip rule" is:a user:997 will work. Note that that wouldn't find answers where you mentioned "ip rule" outside a code block; I think you'd have to run two separate searches to cover both cases.