Ronald Landheer-Cieslak points out that the various back ends which

treat all socket closures as clean exits (because the protocol doesn't
provide for transferring a process exit code) could usefully at least
treat _socket errors_ as unclean exits. Patch the Telnet, Rlogin and
Raw backends to retain that information and return INT_MAX to the
frontend.

I wasn't sure whether it was better to solve this by modifying each
affected frontend, or each affected backend. I chose the latter, but
neither is really ideal; this is the sort of thing that makes me wish
we had a piece of fixed middleware in between, independent of both
platform and protocol.

[originally from svn r9730]

raw.c

@@ -4,6 +4,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <limits.h>
 
 #include "putty.h"
 
@@ -21,6 +22,7 @@ typedef struct raw_backend_data {
     /* the above field _must_ be first in the structure */
 
     Socket s;
+    int closed_on_socket_error;
     int bufsize;
     void *frontend;
     int sent_console_eof, sent_socket_eof;
@@ -75,6 +77,7 @@ static int raw_closing(Plug plug, const char *error_msg, int error_code,
         if (raw->s) {
             sk_close(raw->s);
             raw->s = NULL;
+            raw->closed_on_socket_error = TRUE;
             notify_remote_exit(raw->frontend);
         }
         logevent(raw->frontend, error_msg);
@@ -139,6 +142,7 @@ static const char *raw_init(void *frontend_handle, void **backend_handle,
     raw = snew(struct raw_backend_data);
     raw->fn = &fn_table;
     raw->s = NULL;
+    raw->closed_on_socket_error = FALSE;
     *backend_handle = raw;
     raw->sent_console_eof = raw->sent_socket_eof = FALSE;
 
@@ -306,6 +310,8 @@ static int raw_exitcode(void *handle)
     Raw raw = (Raw) handle;
     if (raw->s != NULL)
         return -1;                     /* still connected */
+    else if (raw->closed_on_socket_error)
+        return INT_MAX;     /* a socket error counts as an unclean exit */
     else
         /* Exit codes are a meaningless concept in the Raw protocol */
         return 0;

rlogin.c

@@ -4,6 +4,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <limits.h>
 #include <ctype.h>
 
 #include "putty.h"
@@ -22,6 +23,7 @@ typedef struct rlogin_tag {
     /* the above field _must_ be first in the structure */
 
     Socket s;
+    int closed_on_socket_error;
     int bufsize;
     int firstbyte;
     int cansize;
@@ -72,6 +74,8 @@ static int rlogin_closing(Plug plug, const char *error_msg, int error_code,
     if (rlogin->s) {
         sk_close(rlogin->s);
         rlogin->s = NULL;
+        if (error_msg)
+            rlogin->closed_on_socket_error = TRUE;
 	notify_remote_exit(rlogin->frontend);
     }
     if (error_msg) {
@@ -175,6 +179,7 @@ static const char *rlogin_init(void *frontend_handle, void **backend_handle,
     rlogin = snew(struct rlogin_tag);
     rlogin->fn = &fn_table;
     rlogin->s = NULL;
+    rlogin->closed_on_socket_error = FALSE;
     rlogin->frontend = frontend_handle;
     rlogin->term_width = conf_get_int(conf, CONF_width);
     rlogin->term_height = conf_get_int(conf, CONF_height);
@@ -392,6 +397,8 @@ static int rlogin_exitcode(void *handle)
     Rlogin rlogin = (Rlogin) handle;
     if (rlogin->s != NULL)
         return -1;                     /* still connected */
+    else if (rlogin->closed_on_socket_error)
+        return INT_MAX;     /* a socket error counts as an unclean exit */
     else
         /* If we ever implement RSH, we'll probably need to do this properly */
         return 0;

telnet.c

@@ -4,6 +4,7 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <limits.h>
 
 #include "putty.h"
 
@@ -181,6 +182,7 @@ typedef struct telnet_tag {
     /* the above field _must_ be first in the structure */
 
     Socket s;
+    int closed_on_socket_error;
 
     void *frontend;
     void *ldisc;
@@ -676,6 +678,8 @@ static int telnet_closing(Plug plug, const char *error_msg, int error_code,
     if (telnet->s) {
         sk_close(telnet->s);
         telnet->s = NULL;
+        if (error_msg)
+            telnet->closed_on_socket_error = TRUE;
 	notify_remote_exit(telnet->frontend);
     }
     if (error_msg) {
@@ -729,6 +733,7 @@ static const char *telnet_init(void *frontend_handle, void **backend_handle,
     telnet->fn = &fn_table;
     telnet->conf = conf_copy(conf);
     telnet->s = NULL;
+    telnet->closed_on_socket_error = FALSE;
     telnet->echoing = TRUE;
     telnet->editing = TRUE;
     telnet->activated = FALSE;
@@ -1096,6 +1101,8 @@ static int telnet_exitcode(void *handle)
     Telnet telnet = (Telnet) handle;
     if (telnet->s != NULL)
         return -1;                     /* still connected */
+    else if (telnet->closed_on_socket_error)
+        return INT_MAX;     /* a socket error counts as an unclean exit */
     else
         /* Telnet doesn't transmit exit codes back to the client */
         return 0;