[Qemu-devel] [PATCH] re-send: enabling TCP keepalives - v5

["David S. Ahern" <daahern@cisco.com>]

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I did not see a response to this a week+ ago. Any objections to this
minimalist version?

david


This patch enables TCP keepalives on VNC connections and TCP-based char
devices.

Changes v4 -> v5
- removed settings for the timers and counter such that OS defaults are
used once the keepalive option is enabled
- enabling keepalives is now an option for TCP char devices
(piggy-backed on the nodelay option Paul mentioned)
- forced on for vnc (making it an option for vnc is a big can of works
that does not need to be opened)

Signed-off-by: David Ahern <dsahern@gmail.com>


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diff --git a/configure b/configure
index 82fb60a..5ce0236 100755
--- a/configure
+++ b/configure
@@ -1673,6 +1673,19 @@ if test "$fdt" = "yes" ; then
   echo "FDT_LIBS=-lfdt" >> $config_mak
 fi
 
+cat > $TMPC << EOF
+#include <sys/socket.h>
+int main(void) {
+  int val = 1;
+  if (setsockopt(0, SOL_SOCKET, SO_KEEPALIVE, &val, sizeof(val)) < 0)
+    return 1;
+  return 0;
+}
+EOF
+if $cc $ARCH_CFLAGS -o $TMPE $TMPC >/dev/null 2> /dev/null ; then
+  echo "#define HAVE_SO_KEEPALIVE 1" >> $config_h
+fi
+
 # XXX: suppress that
 if [ "$bsd" = "yes" ] ; then
   echo "#define O_LARGEFILE 0" >> $config_h
diff --git a/net.c b/net.c
index 7ae1e6d..e787883 100644
--- a/net.c
+++ b/net.c
@@ -2209,3 +2209,18 @@ void net_client_check(void)
                     vlan->id);
     }
 }
+
+int enable_tcp_keepalive(int sd)
+{
+#ifdef HAVE_SO_KEEPALIVE
+    int val = 1;
+
+    if (setsockopt(sd, SOL_SOCKET, SO_KEEPALIVE, &val, sizeof(val)) < 0) {
+        return -1;
+    }
+#else
+    fprintf(stderr, "Warning: TCP keepalives not supported\n");
+#endif
+
+    return 0;
+}
diff --git a/net.h b/net.h
index cdf63a4..29d00fa 100644
--- a/net.h
+++ b/net.h
@@ -119,6 +119,8 @@ void net_client_check(void);
 void net_host_device_add(Monitor *mon, const char *device, const char *opts);
 void net_host_device_remove(Monitor *mon, int vlan_id, const char *device);
 
+int enable_tcp_keepalive(int sd);
+
 #define DEFAULT_NETWORK_SCRIPT "/etc/qemu-ifup"
 #define DEFAULT_NETWORK_DOWN_SCRIPT "/etc/qemu-ifdown"
 #ifdef __sun__
diff --git a/qemu-char.c b/qemu-char.c
index 664cbfd..2d21022 100644
--- a/qemu-char.c
+++ b/qemu-char.c
@@ -1825,6 +1825,7 @@ typedef struct {
     int max_size;
     int do_telnetopt;
     int do_nodelay;
+    int do_keepalive;
     int is_unix;
 } TCPCharDriver;
 
@@ -1998,6 +1999,10 @@ static void tcp_chr_accept(void *opaque)
     socket_set_nonblock(fd);
     if (s->do_nodelay)
         socket_set_nodelay(fd);
+    if (s->do_keepalive && enable_tcp_keepalive(fd) != 0) {
+        fprintf(stderr,
+                "tcp_chr_accept: failed to enable TCP keepalive probes\n");
+    }
     s->fd = fd;
     qemu_set_fd_handler(s->listen_fd, NULL, NULL, NULL);
     tcp_chr_connect(chr);
@@ -2027,6 +2032,7 @@ static CharDriverState *qemu_chr_open_tcp(const char *host_str,
     int is_listen = 0;
     int is_waitconnect = 1;
     int do_nodelay = 0;
+    int do_keepalive = 0;
     const char *ptr;
 
     ptr = host_str;
@@ -2038,6 +2044,8 @@ static CharDriverState *qemu_chr_open_tcp(const char *host_str,
             is_waitconnect = 0;
         } else if (!strncmp(ptr,"nodelay",6)) {
             do_nodelay = 1;
+        } else if (!strncmp(ptr,"keepalive",9) && !is_unix) {
+            do_keepalive = 1;
         } else if (!strncmp(ptr,"to=",3)) {
             /* nothing, inet_listen() parses this one */;
         } else if (!strncmp(ptr,"ipv4",4)) {
@@ -2091,6 +2099,7 @@ static CharDriverState *qemu_chr_open_tcp(const char *host_str,
     s->listen_fd = -1;
     s->is_unix = is_unix;
     s->do_nodelay = do_nodelay && !is_unix;
+    s->do_keepalive = do_keepalive;
 
     chr->opaque = s;
     chr->chr_write = tcp_chr_write;
@@ -2105,6 +2114,10 @@ static CharDriverState *qemu_chr_open_tcp(const char *host_str,
         s->connected = 1;
         s->fd = fd;
         socket_set_nodelay(fd);
+        if (s->do_keepalive && enable_tcp_keepalive(fd) != 0) {
+            fprintf(stderr,
+                    "failed to enable TCP keepalive probes on %d\n", fd);
+        }
         tcp_chr_connect(chr);
     }
 
diff --git a/qemu-options.hx b/qemu-options.hx
index aa786e3..a57e335 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1165,16 +1165,16 @@ telnet on port 5555 to access the qemu port.
 localhost 5555
 @end table
 
-@item tcp:[@var{host}]:@var{port}[,@var{server}][,nowait][,nodelay]
+@item tcp:[@var{host}]:@var{port}[,@var{server}][,nowait][,nodelay][,keepalive]
 The TCP Net Console has two modes of operation.  It can send the serial
 I/O to a location or wait for a connection from a location.  By default
 the TCP Net Console is sent to @var{host} at the @var{port}.  If you use
 the @var{server} option QEMU will wait for a client socket application
 to connect to the port before continuing, unless the @code{nowait}
 option was specified.  The @code{nodelay} option disables the Nagle buffering
-algorithm.  If @var{host} is omitted, 0.0.0.0 is assumed. Only
-one TCP connection at a time is accepted. You can use @code{telnet} to
-connect to the corresponding character device.
+algorithm.  The @code{keepalive} option enables TCP keepalives. If @var{host}
+is omitted, 0.0.0.0 is assumed. Only one TCP connection at a time is accepted.
+You can use @code{telnet} to connect to the corresponding character device.
 @table @code
 @item Example to send tcp console to 192.168.0.2 port 4444
 -serial tcp:192.168.0.2:4444
@@ -1184,7 +1184,7 @@ connect to the corresponding character device.
 -serial tcp:192.168.0.100:4444,server,nowait
 @end table
 
-@item telnet:@var{host}:@var{port}[,server][,nowait][,nodelay]
+@item telnet:@var{host}:@var{port}[,server][,nowait][,nodelay][,keepalive]
 The telnet protocol is used instead of raw tcp sockets.  The options
 work the same as if you had specified @code{-serial tcp}.  The
 difference is that the port acts like a telnet server or client using
diff --git a/vnc.c b/vnc.c
index ab1f044..52af93d 100644
--- a/vnc.c
+++ b/vnc.c
@@ -29,6 +29,7 @@
 #include "qemu_socket.h"
 #include "qemu-timer.h"
 #include "acl.h"
+#include "net.h"
 
 #define VNC_REFRESH_INTERVAL (1000 / 30)
 
@@ -2021,6 +2022,10 @@ static void vnc_listen_read(void *opaque)
 
     int csock = accept(vs->lsock, (struct sockaddr *)&addr, &addrlen);
     if (csock != -1) {
+        if (enable_tcp_keepalive(csock) != 0) {
+            fprintf(stderr, "VNC: failed to enable TCP keepalive probes\n");
+        }
+
         vnc_connect(vs, csock);
     }
 }