Eric Landes provided the patch (edited by me) that introduces the

--keepalive-time to curl to set the keepalive probe interval. I also took
the opportunity to rename the recently added no-keep-alive option to
no-keepalive to keep a consistent naming and to avoid getting two dashes in
these option names. Eric also provided an update to the man page for the new
option.

CHANGES

@@ -6,6 +6,14 @@
 
                                   Changelog
 
+Daniel S (12 Jan 2008)
+- Eric Landes provided the patch (edited by me) that introduces the
+  --keepalive-time to curl to set the keepalive probe interval. I also took
+  the opportunity to rename the recently added no-keep-alive option to
+  no-keepalive to keep a consistent naming and to avoid getting two dashes in
+  these option names. Eric also provided an update to the man page for the new
+  option.
+
 Daniel S (11 Jan 2008)
 - Daniel Egger made CURLOPT_RANGE work on file:// URLs the very same way it
   already worked for FTP:// URLs.

RELEASE-NOTES

@@ -1,7 +1,7 @@
 Curl and libcurl 7.18.0
 
  Public curl releases:         103
- Command line options:         125
+ Command line options:         126
  curl_easy_setopt() options:   150
  Public functions in libcurl:  56
  Public web site mirrors:      42
@@ -12,12 +12,13 @@ This release includes the following changes:
  
  o --data-urlencode
  o CURLOPT_PROXY_TRANSFER_MODE
- o --no-keep-alive - now curl does connections with keep-alive enabled by
+ o --no-keepalive - now curl does connections with keep-alive enabled by
    default
  o --socks4a added (proxy type CURLPROXY_SOCKS4A for libcurl)
  o --socks5-hostname added (CURLPROXY_SOCKS5_HOSTNAME for libcurl)
  o curl_easy_pause()
  o CURLOPT_SEEKFUNCTION and CURLOPT_SEEKDATA
+ o --keepalive-time
 
 This release includes the following bugfixes:
 
@@ -72,6 +73,6 @@ advice from friends like these:
  Emil Romanus, Alessandro Vesely, Ray Pekowski, Spacen Jasset, Andrew Moise,
  Gilles Blanc, David Wright, Vikram Saxena, Mateusz Loskot, Gary Maxwell,
  Dmitry Kurochkin, Mohun Biswas, Richard Atterer, Maxim Perenesenko,
- Daniel Egger, Jeff Johnson, Nikitinskit Dmitriy, Georg Lippitsch
+ Daniel Egger, Jeff Johnson, Nikitinskit Dmitriy, Georg Lippitsch, Eric Landes
  
         Thanks! (and sorry if I forgot to mention someone)

TODO-RELEASE

@@ -4,9 +4,6 @@ To be addressed before 7.18.0 (planned release: January 2008)
 115 - Cleanup debugging messages in test harness, introduced for new minimum
       SSH version support for SCP, SFTP and SOCKS tests
       
-117 - Eric Landes patch for introducing the --tcp-keep* options
-      http://curl.haxx.se/mail/lib-2008-01/0038.html (review, consider)
-
 Less likely to go in 7.18.0
 ===========================
 

docs/curl.1

@@ -612,6 +612,14 @@ See this online resource for further details:
 \fBhttp://curl.haxx.se/docs/sslcerts.html\fP
 
 If this option is used twice, the second time will again disable it.
+.IP "--keepalive-time <seconds>"
+This option sets the time a connection needs to remain idle before sending
+keepalive probes and the time between individual keepalive probes. It is
+currently effective on operating systems offering the TCP_KEEPIDLE and
+TCP_KEEPINTVL socket options (meaning Linux, recent AIX, HP-UX and more). This
+option has no effect if \fI--no-keepalive\fP is used. (Added in 7.18.0)
+
+If this option is used multiple times, the last occurrence sets the amount.
 .IP "--key <key>"
 (SSL/SSH) Private key file name. Allows you to provide your private key in this
 separate file.
@@ -820,11 +828,11 @@ will output the data in chunks, not necessarily exactly when the data arrives.
 Using this option will disable that buffering.
 
 If this option is used twice, the second will again switch on buffering.
-.IP "--no-keep-alive"
+.IP "--no-keepalive"
-Disables the use of keep-alive messages on the TCP connection, as by default
+Disables the use of keepalive messages on the TCP connection, as by default
 curl enables them.
 
-If this option is used twice, the second will again enable keep-alive.
+If this option is used twice, the second will again enable keepalive.
 .IP "--no-sessionid"
 (SSL) Disable curl's use of SSL session-ID caching.  By default all transfers
 are done using the cache. Note that while nothing ever should get hurt by

src/main.c

@@ -104,6 +104,13 @@
 #endif
 #endif /* CURL_DOES_CONVERSIONS && HAVE_ICONV */
 
+#ifdef HAVE_NETINET_IN_H
+#include <netinet/in.h> /* for IPPROTO_TCP */
+#endif
+#ifdef HAVE_NETINET_TCP_H
+#include <netinet/tcp.h> /* for TCP_KEEPIDLE, TCP_KEEPINTVL */
+#endif
+
 /* The last #include file should be: */
 #ifdef CURLDEBUG
 #ifndef CURLTOOLDEBUG
@@ -486,7 +493,9 @@ struct Configurable {
   char *libcurl; /* output libcurl code to this file name */
   bool raw;
   bool post301;
-  bool nokeepalive;
+  bool nokeepalive; /* for keepalive needs */
+  long alivetime;
+
   struct OutStruct *outs;
 };
 
@@ -679,6 +688,7 @@ static void help(void)
     " -I/--head          Show document info only",
     " -j/--junk-session-cookies Ignore session cookies read from file (H)",
     "    --interface <interface> Specify network interface/address to use",
+    "    --keepalive-time <seconds> Interval between keepalive probes",
     "    --krb <level>   Enable kerberos with specified security level (F)",
     " -k/--insecure      Allow connections to SSL sites without certs (H)",
     " -K/--config        Specify which config file to read",
@@ -697,7 +707,7 @@ static void help(void)
     "    --netrc-optional Use either .netrc or URL; overrides -n",
     "    --ntlm          Use HTTP NTLM authentication (H)",
     " -N/--no-buffer     Disable buffering of the output stream",
-    "    --no-keep-alive Disable keep-alive use on the connection",
+    "    --no-keepalive  Disable keepalive use on the connection",
     "    --no-sessionid  Disable SSL session-ID reusing (SSL)",
     " -o/--output <file> Write output to <file> instead of stdout",
     " -O/--remote-name   Write output to a file named as the remote file",
@@ -1444,11 +1454,13 @@ static int ftpcccmethod(struct Configurable *config, char *str)
 }
 
 
-static int set_so_keepalive(void *clientp, curl_socket_t curlfd,
+static int sockoptcallback(void *clientp, curl_socket_t curlfd,
-                            curlsocktype purpose)
+                           curlsocktype purpose)
 {
   struct Configurable *config = (struct Configurable *)clientp;
-  int onoff = config->nokeepalive ? 0 : 1;
+  int onoff = 1; /* this callback is only used if we ask for keepalives on the
+                    connection */
+  long keepidle = config->alivetime;
 
   switch (purpose) {
   case CURLSOCKTYPE_IPCXN:
@@ -1459,6 +1471,28 @@ static int set_so_keepalive(void *clientp, curl_socket_t curlfd,
       warnf(clientp, "Could not set SO_KEEPALIVE!\n");
       return 0;
     }
+    else {
+      if (config->alivetime) {
+#ifdef TCP_KEEPIDLE
+        if(setsockopt(curlfd, IPPROTO_TCP, TCP_KEEPIDLE, (void *)&keepidle,
+                      sizeof(keepidle)) < 0) {
+          /* don't abort operation, just issue a warning */
+          SET_SOCKERRNO(0);
+          warnf(clientp, "Could not set TCP_KEEPIDLE!\n");
+          return 0;
+        }
+#endif
+#ifdef TCP_KEEPINTVL
+        if(setsockopt(curlfd, IPPROTO_TCP, TCP_KEEPINTVL, (void *)&keepidle,
+                      sizeof(keepidle)) < 0) {
+          /* don't abort operation, just issue a warning */
+          SET_SOCKERRNO(0);
+          warnf(clientp, "Could not set TCP_KEEPINTVL!\n");
+          return 0;
+        }
+#endif
+      }
+    }
     break;
   default:
     break;
@@ -1555,8 +1589,9 @@ static ParameterError getparameter(char *flag, /* f or -long-flag */
     {"$z", "libcurl",    TRUE},
     {"$#", "raw",        FALSE},
     {"$0", "post301",    FALSE},
-    {"$1", "no-keep-alive",    FALSE},
+    {"$1", "no-keepalive",   FALSE},
-    {"$2", "socks5-hostname",    TRUE},
+    {"$2", "socks5-hostname", TRUE},
+    {"$3", "keepalive-time",  TRUE},
 
     {"0", "http1.0",     FALSE},
     {"1", "tlsv1",       FALSE},
@@ -2024,9 +2059,13 @@ static ParameterError getparameter(char *flag, /* f or -long-flag */
       case '0': /* --post301 */
         config->post301 ^= TRUE;
         break;
-      case '1': /* --no-keep-alive */
+      case '1': /* --no-keepalive */
         config->nokeepalive ^= TRUE;
         break;
+      case '3': /* --keepalive-time */
+        if(str2num(&config->alivetime, nextarg))
+          return PARAM_BAD_NUMERIC;
+        break;
       }
       break;
     case '#': /* --progress-bar */
@@ -4590,7 +4629,7 @@ operate(struct Configurable *config, int argc, argv_item_t argv[])
         /* curl 7.17.1 */
         my_setopt(curl, CURLOPT_POST301, config->post301);
         if (!config->nokeepalive) {
-          my_setopt(curl, CURLOPT_SOCKOPTFUNCTION, set_so_keepalive);
+          my_setopt(curl, CURLOPT_SOCKOPTFUNCTION, sockoptcallback);
           my_setopt(curl, CURLOPT_SOCKOPTDATA, config);
         }