fix: Minor RPC fixes

[mvadari]

High Level Overview of Change

• ping: The ip field is no longer returned as an empty string for proxied connections without a forwarded-for header. It is now omitted, consistent with the behavior for identified connections.
  • There was also a missing break statement in the proxied connection case block.
• gRPC GetLedgerDiff: Fixed error message that incorrectly said "base ledger not validated" when the desired ledger was not validated.

Context of Change

AI review/triage

BUG-U002: PROXY case unconditionally emits empty ip field unlike IDENTIFIED case

Severity: LOW

In doPing(), the IDENTIFIED case (lines 22-26) conditionally includes the ip field only when context.headers.forwardedFor is non-empty. The PROXY case (lines 28-30) unconditionally writes context.headers.forwardedFor to ret[jss::ip], even when the value is empty. This creates an inconsistency where PROXY connections may return "ip": "" in the response, while IDENTIFIED connections would omit the field entirely. A downstream client parsing the response could misinterpret an empty string as a valid IP address or treat the field's presence as meaningful.

Root cause: Lines 28-30 in Ping.cpp set ret[jss::ip] without checking !context.headers.forwardedFor.empty() first, unlike the analogous check at line 25 for the IDENTIFIED case.

BUG-U001: Missing break in Ping switch causes PROXY case to fall through to default

Severity: LOW

In doPing(), the switch statement on context.role handles Role::PROXY at line 28-30 but is missing a break statement. The case falls through directly to default:;. Currently the default case is an empty statement, so there is no behavioral change. However, this is a classic C++ switch-fallthrough bug pattern that violates defensive coding practices. If a future maintainer adds any logic to the default case (e.g., error logging, default field values), the PROXY case would silently execute that code as well, leading to unexpected behavior.

Root cause: The case Role::PROXY: block at line 28-30 in Ping.cpp does not end with a break statement. The case Role::IDENTIFIED: block above it correctly has a break at line 27, making the omission in the PROXY case clearly unintentional rather than a deliberate fallthrough pattern.

BUG-U004: Wrong error message for desired ledger in doLedgerDiffGrpc

Severity: LOW

When the desired ledger's dynamic_pointer_cast fails in doLedgerDiffGrpc, the error message incorrectly states 'base ledger not validated' instead of 'desired ledger not validated'. This misleads API consumers about which ledger parameter caused the error.

Root cause: LedgerDiff.cpp line 39: the error message string was copy-pasted from the base ledger check (line 31) without updating the text.

API Impact

Minor bugfixes, no API format change.

[Copilot]

Pull request overview

This PR applies small correctness fixes to RPC responses and gRPC error reporting, improving consistency and clarity for API consumers.

Changes:

• ping: Omit the ip field for proxied connections when no forwarded-for header is present, and add the missing break in the Role::PROXY switch case.
• gRPC GetLedgerDiff: Correct the NOT_FOUND error message when the desired ledger is not validated.
• Add/adjust tests and document the behavior in the API changelog.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/xrpld/rpc/handlers/utility/Ping.cpp	Fixes proxied ping response consistency and prevents switch fallthrough.
src/xrpld/rpc/handlers/ledger/LedgerDiff.cpp	Fixes misleading gRPC error message for unvalidated desired ledger.
src/test/rpc/Roles_test.cpp	Adds regression coverage ensuring proxied ping omits ip when absent.
API-CHANGELOG.md	Documents the ping and gRPC LedgerDiff bugfixes.

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[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.4%. Comparing base (077e03f) to head (9ebccf9).
⚠️ Report is 1 commits behind head on develop.

Files with missing lines	Patch %	Lines
src/xrpld/rpc/handlers/ledger/LedgerDiff.cpp	0.0%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #6730     +/-   ##
=========================================
- Coverage     81.5%   81.4%   -0.0%     
=========================================
  Files         1006    1006             
  Lines        74461   74463      +2     
  Branches      7582    7557     -25     
=========================================
- Hits         60651   60640     -11     
- Misses       13810   13823     +13     

Files with missing lines	Coverage Δ
src/xrpld/rpc/handlers/utility/Ping.cpp	100.0% <100.0%> (ø)
src/xrpld/rpc/handlers/ledger/LedgerDiff.cpp	0.0% <0.0%> (ø)

... and 4 files with indirect coverage changes

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