Lcos-000 opened a new issue, #3683:
URL: https://github.com/apache/dubbo-go/issues/3683
### Description
Follow-up to #3680.
`RPCInvocation.ActualMethodName()`
(`protocol/invocation/rpcinvocation.go:85-91`) performs an unguarded type
assertion on the first generic-call argument:
```go
func (r *RPCInvocation) ActualMethodName() string {
if r.IsGenericInvocation() {
return r.Arguments()[0].(string) // panics if arg[0] is not a
string
} else {
return r.MethodName()
}
}
```
`IsGenericInvocation()` only checks `len(Arguments)==3`, not the element
types. A malformed `$invoke` with a non-string `arg[0]` reaches this line and
panics with `interface conversion: interface {} is X, not string`.
### Reproduction
```go
inv := invocation.NewRPCInvocation(constant.Generic,
[]any{123, []string{}, []hessian.Object{}},
map[string]{constant.GenericKey: "true"})
// inv.ActualMethodName() -> panic: interface conversion: interface {} is
int, not string
```
### Reachability
In the default `DefaultServiceFilters` chain, `genericServiceFilter` (fixed
by #3680) runs **before** `otelServerFilter` and short-circuits malformed
invocations, so `ActualMethodName()` is not reached. This is therefore **not
reachable by default**.
However, `otelServerFilter` is appended to the filter chain when
`otel.tracing.enable=true` (`server/action.go:388-389`), and the filter order
is user-configurable via the service/provider `filter` setting
(`server/action.go:380`). If a user places `otelServerTrace` before
`generic_service`, or omits `generic_service` from a custom chain, the panic
becomes reachable on the only server-side call site
(`filter/otel/trace/filter.go:83`).
The remaining 6 call sites are client-side (cluster invokers / loadbalance)
and handle locally-constructed invocations, so they are not externally
reachable.
### Affected call sites
| Location | Side | Reachable? |
|---|---|---|
| `filter/otel/trace/filter.go:83` (otelServerFilter.Invoke) | server | Only
with non-default filter ordering + tracing enabled |
| `filter/otel/trace/filter.go:126` (otelClientFilter.Invoke) | client | No |
| `cluster/cluster/failover/cluster_invoker.go:64` | client | No |
| `cluster/cluster/failfast/cluster_invoker.go:49` | client | No |
| `cluster/cluster/forking/cluster_invoker.go:66` | client | No |
| `cluster/cluster/zoneaware/cluster_invoker.go:88` | client | No |
| `cluster/loadbalance/p2c/loadbalance.go:118` | client | No |
### Environment
- dubbo-go version: `develop` @ `9757e773`
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