Add two new unpcb flags, UNP_BINDING and UNP_CONNECTING, which will be

used to mark UNIX domain sockets as being in the process of binding or
connecting.  Use these to prevent simultaneous bind or connect
operations by multiple threads or processes on the same socket at the
same time, which closes race conditions present in the UNIX domain
socket implementation since inception.

1 files changed, 8 insertions, 0 deletions

diff --git a/sys/sys/unpcb.h b/sys/sys/unpcb.h
index a1186de..b910f03 100644
--- a/sys/sys/unpcb.h
+++ b/sys/sys/unpcb.h
@@ -98,6 +98,14 @@ struct unpcb {
 #define	UNP_WANTCRED			0x004	/* credentials wanted */
 #define	UNP_CONNWAIT			0x008	/* connect blocks until accepted */
 
+/*
+ * These flags are used to handle non-atomicity in connect() and bind()
+ * operations on a socket: in particular, to avoid races between multiple
+ * threads or processes operating simultaneously on the same socket.
+ */
+#define	UNP_CONNECTING			0x010	/* Currently connecting. */
+#define	UNP_BINDING			0x020	/* Currently binding. */
+
 #define	sotounpcb(so)	((struct unpcb *)((so)->so_pcb))
 
 /* Hack alert -- this structure depends on <sys/socketvar.h>. */