so_rerror

[christos%zoulas.com@localhost (Christos Zoulas)]

Hello,

Since the introduction of so_rerror tracking to detect receive
socket overflows, we have been trying to make other programs cope
by increasing their buffer sizes and avoid the error message flood.
We have taken this as far as it goes now, and still there are
pathological cases where the new behavior cannot easily be fixed
(one has to go and fix each program separately). One example is
when a program turns on debugging to syslog and logs quicker than
syslog can absorb. What happens then is that syslog and the program
keep spewing error messages about the socket overflow and do little
else...

While keeping track of receive overflows maybe desired (in the
routing socket + dhcpcd case), I think since it is a new behavior
it should be optional; programs that want to know about it should
turn it on. This patch restores the original behavior and allows
program who care about receive errors to arrange to be notified by
introducing setsockopt SO_RERROR.

Best,

christos

Index: kern/uipc_socket.c
===================================================================
RCS file: /cvsroot/src/sys/kern/uipc_socket.c,v
retrieving revision 1.265
diff -u -u -r1.265 uipc_socket.c
--- kern/uipc_socket.c	3 Sep 2018 16:29:35 -0000	1.265
+++ kern/uipc_socket.c	3 Nov 2018 15:22:19 -0000
@@ -1757,6 +1757,7 @@
 	case SO_OOBINLINE:
 	case SO_TIMESTAMP:
 	case SO_NOSIGPIPE:
+	case SO_RERROR:
 #ifdef SO_OTIMESTAMP
 	case SO_OTIMESTAMP:
 #endif
@@ -1958,6 +1959,7 @@
 	case SO_OOBINLINE:
 	case SO_TIMESTAMP:
 	case SO_NOSIGPIPE:
+	case SO_RERROR:
 #ifdef SO_OTIMESTAMP
 	case SO_OTIMESTAMP:
 #endif
Index: kern/uipc_socket2.c
===================================================================
RCS file: /cvsroot/src/sys/kern/uipc_socket2.c,v
retrieving revision 1.132
diff -u -u -r1.132 uipc_socket2.c
--- kern/uipc_socket2.c	3 Sep 2018 16:29:35 -0000	1.132
+++ kern/uipc_socket2.c	3 Nov 2018 15:22:19 -0000
@@ -509,7 +509,8 @@
 	KASSERT(solocked(so));
 
 	so->so_rcv.sb_overflowed++;
-	so->so_rerror = ENOBUFS;
+	if (so->so_options & SO_RERROR) 
+		so->so_rerror = ENOBUFS;
 	sorwakeup(so);
 }
 
===================================================================
RCS file: /cvsroot/src/sys/sys/socket.h,v
retrieving revision 1.128
diff -u -u -r1.128 socket.h
--- sys/socket.h	16 Sep 2018 20:40:20 -0000	1.128
+++ sys/socket.h	3 Nov 2018 15:22:19 -0000
@@ -132,6 +132,7 @@
 #define	SO_NOSIGPIPE	0x0800		/* no SIGPIPE from EPIPE */
 #define	SO_ACCEPTFILTER	0x1000		/* there is an accept filter */
 #define	SO_TIMESTAMP	0x2000		/* timestamp received dgram traffic */
+#define	SO_RERROR	0x4000		/* Keep track of receive errors */
 
 
 /*