From 102ea03373d20f59d1933a3c06e255575c8e8b8b Mon Sep 17 00:00:00 2001
From: Robert Watson <rwatson@FreeBSD.org>
Date: Tue, 25 Apr 2006 11:48:16 +0000
Subject: [PATCH] Extend getsock() to return the struct file flags read while
 holding the file lock, in the style of fgetsock().

Modify accept1() to use getsock() instead of fgetsock(), relying on the
file descriptor reference rather than an acquired socket reference to
prevent the listen socket from being destroyed during accept().  This
avoids additional reference count operations, which should improve
performance, and also avoids accept1() operating on a socket whose file
descriptor has been torn down, which may have resulted in protocol
shutdown starting.

MFC after:	3 months
---
 sys/kern/uipc_syscalls.c | 37 +++++++++++++++++++------------------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/sys/kern/uipc_syscalls.c b/sys/kern/uipc_syscalls.c
index 4147409c9df..cb47c307942 100644
--- a/sys/kern/uipc_syscalls.c
+++ b/sys/kern/uipc_syscalls.c
@@ -105,10 +105,11 @@ SYSCTL_INT(_kern_ipc, OID_AUTO, nsfbufsused, CTLFLAG_RD, &nsfbufsused, 0,
  * file entry is held upon returning.  This is lighter weight than
  * fgetsock(), which bumps the socket reference drops the file reference
  * count instead, as this approach avoids several additional mutex operations
- * associated with the additional reference count.
+ * associated with the additional reference count.  If requested, return the
+ * open file flags.
  */
 static int
-getsock(struct filedesc *fdp, int fd, struct file **fpp)
+getsock(struct filedesc *fdp, int fd, struct file **fpp, u_int *fflagp)
 {
 	struct file *fp;
 	int error;
@@ -126,6 +127,8 @@ getsock(struct filedesc *fdp, int fd, struct file **fpp)
 			error = ENOTSOCK;
 		} else {
 			fhold(fp);
+			if (fflagp != NULL)
+				*fflagp = fp->f_flag;
 			error = 0;
 		}
 		FILEDESC_UNLOCK_FAST(fdp);
@@ -221,7 +224,7 @@ kern_bind(td, fd, sa)
 	int error;
 
 	NET_LOCK_GIANT();
-	error = getsock(td->td_proc->p_fd, fd, &fp);
+	error = getsock(td->td_proc->p_fd, fd, &fp, NULL);
 	if (error)
 		goto done2;
 	so = fp->f_data;
@@ -260,7 +263,7 @@ listen(td, uap)
 	int error;
 
 	NET_LOCK_GIANT();
-	error = getsock(td->td_proc->p_fd, uap->s, &fp);
+	error = getsock(td->td_proc->p_fd, uap->s, &fp, NULL);
 	if (error == 0) {
 		so = fp->f_data;
 #ifdef MAC
@@ -283,9 +286,6 @@ done:
 /*
  * accept1()
  * MPSAFE
- *
- * XXXRW: Use getsock() instead of fgetsock() here to avoid additional mutex
- * operations due to soref()/sorele().
  */
 static int
 accept1(td, uap, compat)
@@ -298,7 +298,7 @@ accept1(td, uap, compat)
 	int compat;
 {
 	struct filedesc *fdp;
-	struct file *nfp = NULL;
+	struct file *headfp, *nfp = NULL;
 	struct sockaddr *sa = NULL;
 	socklen_t namelen;
 	int error;
@@ -317,9 +317,10 @@ accept1(td, uap, compat)
 			return (EINVAL);
 	}
 	NET_LOCK_GIANT();
-	error = fgetsock(td, uap->s, &head, &fflag);
+	error = getsock(fdp, uap->s, &headfp, &fflag);
 	if (error)
 		goto done2;
+	head = headfp->f_data;
 	if ((head->so_options & SO_ACCEPTCONN) == 0) {
 		error = EINVAL;
 		goto done;
@@ -453,7 +454,7 @@ noconnection:
 done:
 	if (nfp != NULL)
 		fdrop(nfp, td);
-	fputsock(head);
+	fdrop(headfp, td);
 done2:
 	NET_UNLOCK_GIANT();
 	return (error);
@@ -521,7 +522,7 @@ kern_connect(td, fd, sa)
 	int interrupted = 0;
 
 	NET_LOCK_GIANT();
-	error = getsock(td->td_proc->p_fd, fd, &fp);
+	error = getsock(td->td_proc->p_fd, fd, &fp, NULL);
 	if (error)
 		goto done2;
 	so = fp->f_data;
@@ -740,7 +741,7 @@ kern_sendit(td, s, mp, flags, control, segflg)
 #endif
 
 	NET_LOCK_GIANT();
-	error = getsock(td->td_proc->p_fd, s, &fp);
+	error = getsock(td->td_proc->p_fd, s, &fp, NULL);
 	if (error)
 		goto bad2;
 	so = (struct socket *)fp->f_data;
@@ -952,7 +953,7 @@ kern_recvit(td, s, mp, namelenp, segflg, controlp)
 		*controlp = 0;
 
 	NET_LOCK_GIANT();
-	error = getsock(td->td_proc->p_fd, s, &fp);
+	error = getsock(td->td_proc->p_fd, s, &fp, NULL);
 	if (error) {
 		NET_UNLOCK_GIANT();
 		return (error);
@@ -1282,7 +1283,7 @@ shutdown(td, uap)
 	int error;
 
 	NET_LOCK_GIANT();
-	error = getsock(td->td_proc->p_fd, uap->s, &fp);
+	error = getsock(td->td_proc->p_fd, uap->s, &fp, NULL);
 	if (error == 0) {
 		so = fp->f_data;
 		error = soshutdown(so, uap->how);
@@ -1349,7 +1350,7 @@ kern_setsockopt(td, s, level, name, val, valseg, valsize)
 	}
 
 	NET_LOCK_GIANT();
-	error = getsock(td->td_proc->p_fd, s, &fp);
+	error = getsock(td->td_proc->p_fd, s, &fp, NULL);
 	if (error == 0) {
 		so = fp->f_data;
 		error = sosetopt(so, &sopt);
@@ -1432,7 +1433,7 @@ kern_getsockopt(td, s, level, name, val, valseg, valsize)
 	}
 
 	NET_LOCK_GIANT();
-	error = getsock(td->td_proc->p_fd, s, &fp);
+	error = getsock(td->td_proc->p_fd, s, &fp, NULL);
 	if (error == 0) {
 		so = fp->f_data;
 		error = sogetopt(so, &sopt);
@@ -1466,7 +1467,7 @@ getsockname1(td, uap, compat)
 	int error;
 
 	NET_LOCK_GIANT();
-	error = getsock(td->td_proc->p_fd, uap->fdes, &fp);
+	error = getsock(td->td_proc->p_fd, uap->fdes, &fp, NULL);
 	if (error)
 		goto done2;
 	so = fp->f_data;
@@ -1554,7 +1555,7 @@ getpeername1(td, uap, compat)
 	int error;
 
 	NET_LOCK_GIANT();
-	error = getsock(td->td_proc->p_fd, uap->fdes, &fp);
+	error = getsock(td->td_proc->p_fd, uap->fdes, &fp, NULL);
 	if (error)
 		goto done2;
 	so = fp->f_data;