[PATCH usbredirserver] usbredirserver : enable TCP keepalive

["zhenwei.pi" <zhenwei.pi@xxxxxxxxxxxxxxx>]

In some bad cases, for example, host OS crashes without
sending any FIN to usbredirserver, and usbredirserver
will keep idle connection for a long time.

We can also set the kernel arguments, it means that other
processes may be affected.

Setting a sensible timeout(like 10 minutes) seems good.
But QEMU is restarted after host OS crashes, it usually
needs to reconnect usbredirserver within 2 minutes.

So, add cmdline argument '-k' and "--keepalive" for
usbredirserver to set tcp keepalive idle time.

If setting TCP keepalive fails with errno ENOTSUP, ignore
the specific error.

Signed-off-by: zhenwei.pi <zhenwei.pi@xxxxxxxxxxxxxxx>
---
 usbredirserver/usbredirserver.c | 31 ++++++++++++++++++++++++++++++-
 1 file changed, 30 insertions(+), 1 deletion(-)

diff --git a/usbredirserver/usbredirserver.c b/usbredirserver/usbredirserver.c
index 5575181..3a7620a 100644
--- a/usbredirserver/usbredirserver.c
+++ b/usbredirserver/usbredirserver.c
@@ -37,6 +37,7 @@
 #include <netdb.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
+#include <netinet/tcp.h>
 #include "usbredirhost.h"
 
 
@@ -52,6 +53,7 @@ static const struct option longopts[] = {
     { "verbose", required_argument, NULL, 'v' },
     { "ipv4", required_argument, NULL, '4' },
     { "ipv6", required_argument, NULL, '6' },
+    { "keepalive", required_argument, NULL, 'k' },
     { "help", no_argument, NULL, 'h' },
     { NULL, 0, NULL, 0 }
 };
@@ -98,6 +100,7 @@ static void usage(int exit_code, char *argv0)
     fprintf(exit_code? stderr:stdout,
         "Usage: %s [-p|--port <port>] [-v|--verbose <0-5>] "
         "[[-4|--ipv4 ipaddr]|[-6|--ipv6 ipaddr]] "
+        "[-k|--keepalive time] "
         "<busnum-devnum|vendorid:prodid>\n",
         argv0);
     exit(exit_code);
@@ -203,6 +206,7 @@ int main(int argc, char *argv[])
     int usbvendor  = -1;
     int usbproduct = -1;
     int on = 1;
+    int keepalive  = -1;
     char *ipv4_addr = NULL, *ipv6_addr = NULL;
     union {
         struct sockaddr_in v4;
@@ -211,7 +215,7 @@ int main(int argc, char *argv[])
     struct sigaction act;
     libusb_device_handle *handle = NULL;
 
-    while ((o = getopt_long(argc, argv, "hp:v:4:6:", longopts, NULL)) != -1) {
+    while ((o = getopt_long(argc, argv, "hp:v:4:6:k:", longopts, NULL)) != -1) {
         switch (o) {
         case 'p':
             port = strtol(optarg, &endptr, 10);
@@ -233,6 +237,13 @@ int main(int argc, char *argv[])
         case '6':
             ipv6_addr = optarg;
             break;
+        case 'k':
+            keepalive = strtol(optarg, &endptr, 10);
+            if (*endptr != '\0') {
+                fprintf(stderr, "Invalid value for --keepalive: '%s'\n", optarg);
+                usage(1, argv[0]);
+            }
+            break;
         case '?':
         case 'h':
             usage(o == '?', argv[0]);
@@ -348,6 +359,24 @@ int main(int argc, char *argv[])
             break;
         }
 
+        if (keepalive > 0) {
+            int optval = 1;
+            socklen_t optlen = sizeof(optval);
+            if (setsockopt(client_fd, SOL_SOCKET, SO_KEEPALIVE, &optval, optlen) == -1) {
+                if (errno != ENOTSUP) {
+                    perror("setsockopt SO_KEEPALIVE error.");
+                    break;
+                }
+            }
+            optval = keepalive;
+            if (setsockopt(client_fd, SOL_TCP, TCP_KEEPIDLE, &optval, optlen) == -1) {
+                if (errno != ENOTSUP) {
+                    perror("setsockopt TCP_KEEPIDLE error.");
+                    break;
+                }
+            }
+        }
+
         flags = fcntl(client_fd, F_GETFL);
         if (flags == -1) {
             perror("fcntl F_GETFL");
-- 
2.7.4

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