Cap SMB TCP burst at 4×MSS to stay under NE2000 RX ring (#371)

This commit is contained in:
Felix Rieseberg
2026-04-14 16:50:19 -07:00
committed by GitHub
parent b14ea86ced
commit d0090e5569

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@@ -142,8 +142,10 @@ export function setupSmbShare(emulator: V86, hostPath: string | null, toolsRoot?
} }
// v86's TCP is stop-and-wait (one MSS, wait for ACK). The link is lossless // v86's TCP is stop-and-wait (one MSS, wait for ACK). The link is lossless
// and has no retransmit anyway, so keep a window in flight by sliding the // and has no retransmit anyway, so keep a small window in flight by sliding
// ring-buffer view under the original pump(). 8×MSS cap ≈ NE2000 RX ring. // the ring-buffer view under the original pump(). The burst lands in the
// NE2000 RX ring before the guest CPU runs, so the cap is the ring (5258
// pages for Win95's driver) — 4×MSS + our ACK ≈ 36 pages, 8 overflowed it.
const c = conn as any, sb = c.send_buffer; const c = conn as any, sb = c.send_buffer;
const mss: number = c.send_chunk_buf?.length ?? 1460; const mss: number = c.send_chunk_buf?.length ?? 1460;
const pump1 = Object.getPrototypeOf(c)?.pump; const pump1 = Object.getPrototypeOf(c)?.pump;
@@ -152,7 +154,7 @@ export function setupSmbShare(emulator: V86, hostPath: string | null, toolsRoot?
c.pump = function () { c.pump = function () {
if (this.pending || !sb.length) return pump1.call(this); if (this.pending || !sb.length) return pump1.call(this);
const cap = sb.buffer.length, t0 = sb.tail, l0 = sb.length, s0 = this.seq; const cap = sb.buffer.length, t0 = sb.tail, l0 = sb.length, s0 = this.seq;
const win = Math.max(mss, Math.min(this.winsize || 8192, 8 * mss)); const win = 4 * mss;
let off = hi === undefined ? 0 : Math.max(0, Math.min(hi - s0, l0)); let off = hi === undefined ? 0 : Math.max(0, Math.min(hi - s0, l0));
for (; off < l0 && off < win; off += Math.min(mss, l0 - off)) { for (; off < l0 && off < win; off += Math.min(mss, l0 - off)) {
sb.tail = (t0 + off) % cap; sb.length = l0 - off; sb.tail = (t0 + off) % cap; sb.length = l0 - off;