From e35d20f79c4604c41a3b912b41aae322adf96bc7 Mon Sep 17 00:00:00 2001
From: Kevin Krakauer <krakauer@google.com>
Date: Mon, 12 Jul 2021 22:34:44 -0700
Subject: netstack: move SO_SNDBUF/RCVBUF clamping logic out of //pkg/tcpip

- Keeps Linux-specific behavior out of //pkg/tcpip
- Makes it clearer that clamping is done only for setsockopt calls from users
- Removes code duplication

PiperOrigin-RevId: 384389809
---
 pkg/sentry/socket/netstack/netstack.go | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

(limited to 'pkg/sentry/socket/netstack')

diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index 5d5c4ebbd..ea736e446 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -1682,6 +1682,26 @@ func SetSockOpt(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, level int
 	return nil
 }
 
+func clampBufSize(newSz, min, max int64) int64 {
+	// packetOverheadFactor is used to multiply the value provided by the user on
+	// a setsockopt(2) for setting the send/receive buffer sizes sockets.
+	const packetOverheadFactor = 2
+
+	if newSz > max {
+		newSz = max
+	}
+
+	if newSz < math.MaxInt32/packetOverheadFactor {
+		newSz *= packetOverheadFactor
+		if newSz < min {
+			newSz = min
+		}
+	} else {
+		newSz = math.MaxInt32
+	}
+	return newSz
+}
+
 // setSockOptSocket implements SetSockOpt when level is SOL_SOCKET.
 func setSockOptSocket(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, name int, optVal []byte) *syserr.Error {
 	switch name {
@@ -1691,7 +1711,9 @@ func setSockOptSocket(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, nam
 		}
 
 		v := hostarch.ByteOrder.Uint32(optVal)
-		ep.SocketOptions().SetSendBufferSize(int64(v), true /* notify */)
+		min, max := ep.SocketOptions().SendBufferLimits()
+		clamped := clampBufSize(int64(v), min, max)
+		ep.SocketOptions().SetSendBufferSize(clamped, true /* notify */)
 		return nil
 
 	case linux.SO_RCVBUF:
@@ -1700,7 +1722,9 @@ func setSockOptSocket(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, nam
 		}
 
 		v := hostarch.ByteOrder.Uint32(optVal)
-		ep.SocketOptions().SetReceiveBufferSize(int64(v), true /* notify */)
+		min, max := ep.SocketOptions().ReceiveBufferLimits()
+		clamped := clampBufSize(int64(v), min, max)
+		ep.SocketOptions().SetReceiveBufferSize(clamped, true /* notify */)
 		return nil
 
 	case linux.SO_REUSEADDR:
-- 
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