denoland/deno · error · TypeError

ERR_SOCKET_BAD_BUFFER_SIZE

ERR_SOCKET_BAD_BUFFER_SIZE

Error message

Buffer size must be a positive integer

What it means

Backing validation for dgram Socket.setRecvBufferSize/setSendBufferSize (via the internal bufferSize() helper): the size is coerced with 'size >>> 0' and must round-trip exactly, i.e. be a uint32. Negative numbers, fractional values, NaN, Infinity, and anything above 0xFFFFFFFF fail the check and throw ERR_SOCKET_BAD_BUFFER_SIZE.

Source

Thrown at ext/node/polyfills/dgram.ts:1403

function replaceHandle(self: Socket, newHandle: UDP) {
  const state = self[kStateSymbol];
  const oldHandle = state.handle!;

  // Set up the handle that we got from primary.
  newHandle.lookup = oldHandle.lookup;
  newHandle.bind = oldHandle.bind;
  newHandle.send = oldHandle.send;
  newHandle[ownerSymbol] = self;

  // Replace the existing handle by the handle we got from primary.
  oldHandle.close();
  state.handle = newHandle;
}

function bufferSize(self: Socket, size: number, buffer: boolean): number {
  if (size >>> 0 !== size) {
    throw new ERR_SOCKET_BAD_BUFFER_SIZE();
  }

  const ctx = {};
  const ret = self[kStateSymbol].handle!.bufferSize(size, buffer, ctx);

  if (ret === undefined) {
    throw new ERR_SOCKET_BUFFER_SIZE(ctx as NodeSystemErrorCtx);
  }

  return ret;
}

function socketCloseNT(self: Socket) {
  self.emit("close");
}

function healthCheck(socket: Socket) {
  if (!socket[kStateSymbol].handle) {

View on GitHub (pinned to 89f33cbef2)

Solutions

1. Sanitize to a non-negative integer before calling: Math.max(0, Math.floor(Number(size))) and verify !Number.isNaN
2. Use Number.isInteger(size) && size >= 0 && size <= 0xFFFFFFFF as a guard for values from untrusted sources
3. Pick a sane default (e.g. 4096..262144) when the configured value fails validation

Example fix

// before
const size = parseInt(process.env.SO_RCVBUF); // NaN if unset/malformed
sock.setRecvBufferSize(size); // throws ERR_SOCKET_BAD_BUFFER_SIZE

// after
const size = Number.parseInt(process.env.SO_RCVBUF, 10);
sock.setRecvBufferSize(Number.isInteger(size) && size > 0 ? size : 65536);

function safeBufferSize(v, fallback = 65536) {
  const n = Math.floor(Number(v));
  return Number.isInteger(n) && n >= 0 && n <= 0xFFFFFFFF ? n : fallback;
}
sock.setRecvBufferSize(safeBufferSize(config.recvBuf));

function isU32(v) { return typeof v === 'number' && Number.isInteger(v) && v >= 0 && v <= 0xFFFFFFFF; }

When it happens

Trigger: socket.setRecvBufferSize(65536.5); socket.setSendBufferSize(-1); socket.setRecvBufferSize(NaN) (e.g. a failed parseInt); setRecvBufferSize(2 ** 33); passing a string like '65536'.

Common situations: Reading buffer sizes from config/env without numeric validation; computing sizes with division or scaling that yields fractions; parseInt returning NaN on malformed input.

Related errors

• ERR_INVALID_ARG_TYPE
• ERR_SOCKET_BUFFER_SIZE
• ERR_SOCKET_DGRAM_NOT_RUNNING
• resolve hook must return { shortCircuit: true } or call next
• load hook must return { shortCircuit: true } or call nextLoa

AI-assisted analysis of denoland/deno@89f33cbef2 (2026-08-16). Data as JSON: /api/errors/af76ea75c24d086f. Report an issue: GitHub.