-sNODERAWSOCKETS DNS resolution, with general readiness - #27182
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Does this change actually depend on the epoll implementation? |
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Formally speaking, it doesn't, but to integrate the non-JSPI support, the ability to associate a callback with the file descriptor readiness comes from the epoll PR, which previously required a custom callback integration. |
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Under -sNODERAWSOCKETS, getaddrinfo() previously fabricated fake addresses via DNS.lookup_name. This adds real resolution backed by node:dns, plus an async getaddrinfo so names can be resolved without blocking. getaddrinfo() now resolves numeric addresses and /etc/hosts entries (read fresh through emscripten's FS) synchronously, and returns a full addrinfo list (one node per address). For a real hostname: - without JSPI it returns EAI_AGAIN (no synchronous DNS); resolve it via the async API below. - under JSPI it suspends the wasm stack on the node:dns lookup and returns the addresses directly (gated on ASYNCIFY == 2). The async API (available in all builds): - emscripten_dns_lookup_async(node, service, hint) takes the same inputs as getaddrinfo() and returns a pollable fd that becomes readable when resolution completes. - emscripten_dns_lookup_result(fd, struct addrinfo **res) reads the outcome: 0 on success (writing the addrinfo list to *res, freed with freeaddrinfo), or an EAI_* code on failure. The completion fd is a plain pollable descriptor: wait on it with epoll/poll/select. freeaddrinfo now frees the whole ai_next chain; EAI_AGAIN is added to the generated struct info. Tested with test_dns_async, test_dns_async_net, test_dns_async_default, and test_dns_jspi, including PROXY_TO_PTHREAD variants.
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This gives `getaddrinfo()` real name resolution under `-sNODERAWSOCKETS`. Split out from #27182, which also added a new asynchronous DNS API; this PR is only the change to the existing blocking API, allowing any async API work to follow separately. Previously every hostname resolved to a fake `172.29.x.x` address, which is fine for the websocket proxy transport but not for real Node.js sockets, where the address has to be connectable. * Hostnames resolve via `node:dns` (which honors the host's `/etc/hosts`). The lookup is asynchronous, so `getaddrinfo` blocks by returning a Promise where the calling stack can wait on it: a sync-proxied pthread (`PROXY_SYNC_ASYNC`, e.g. `main()` under `PROXY_TO_PTHREAD`), or `ASYNCIFY`/`JSPI` by suspending through `Asyncify.handleAsync`, which also holds a runtime keepalive so a user callback completing mid-lookup does not exit the runtime. Numeric addresses and errors still return synchronously, so `JSPI` does not pay a microtask on those. * Where there is no stack that can wait (the event-loop thread itself), a hostname returns `EAI_AGAIN` without starting a lookup. * Results may now be an `addrinfo` linked list (multiple DNS records, `AF_UNSPEC`), and `freeaddrinfo` walks the whole chain. Everything is gated on `NODERAWSOCKETS`; without it `getaddrinfo` is unchanged. Implementation-wise `getaddrinfo` keeps its existing body and returns either an `EAI_*` code or a Promise of one. The pthread proxy receive side now accepts a synchronous value from a `PROXY_SYNC_ASYNC` function (`Promise.resolve(rtn).then(...)`), so no wrapper is needed for the sync paths. Tested with `test_noderawsockets_dns` (numeric, `EAI_AGAIN` single-threaded), and `test_noderawsockets_dns_blocking{,_asyncify,_jspi}` (multi-address lists across families, and a timer firing during the lookup under `EXIT_RUNTIME`).
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Async DNS, built on top of #27207 for async readiness. Implementation diff is the last commit - b5af97b.
This adds real DNS resolution under
-sNODERAWSOCKETSvianode:dns, along with an async syscall variant ofgetaddrinfofor non-JSPI environments.getaddrinfo()resolves numeric addresses and/etc/hostsentries (read fresh through emscripten's FS) synchronously, and returns a fulladdrinfolist. For a real hostname: without JSPI it returnsEAI_AGAIN(resolve via the async API); under JSPI it suspends the wasm stack on thenode:dnslookup and returns the addresses directly.Async API (available in all builds):
emscripten_dns_lookup_async(node, service, hint)— same inputs asgetaddrinfo(), returns a pollable fd that becomes readable when resolution completes.emscripten_dns_lookup_result(fd, struct addrinfo **res)— reads the outcome:0on success (writing theaddrinfolist to*res, freed withfreeaddrinfo), or anEAI_*code.The original PR in #27162 allowed the async callback for DNS lookup to be registered via
emscripten_set_socket_message_callback. Instead of "hijacking" that mechanism, we can now directly use an epoll'able file descriptor to represent the dns lookup operation. On readiness, the actualemscripten_dns_lookup_result()just gets called again.freeaddrinfonow frees the wholeai_nextchain;EAI_AGAINis added to the generated struct info.Tested with
test_dns_async,test_dns_callback(completion viaemscripten_poll_with_callback),test_dns_async_net,test_dns_async_default, andtest_dns_jspi, includingPROXY_TO_PTHREADvariants.