qrexec: when forgetting about a client/process, flush buffered data

We need to spawn a child to take care of buffered data flushing, if there
is any. Expensive, but should be needed rarely.

qrexec/Makefile

@@ -6,8 +6,8 @@ COMMONIOALL=../common/ioall.o
 all: qrexec_daemon qrexec_agent qrexec_client
 qrexec_daemon: qrexec_daemon.o unix_server.o $(COMMONIOALL) txrx-vchan.o buffer.o write_stdin.o
 	$(CC) -g -o qrexec_daemon qrexec_daemon.o unix_server.o $(COMMONIOALL) txrx-vchan.o write_stdin.o buffer.o $(XENLIBS)
-qrexec_agent: qrexec_agent.o exec.o txrx-vchan.o write_stdin.o buffer.o
+qrexec_agent: qrexec_agent.o exec.o txrx-vchan.o write_stdin.o buffer.o $(COMMONIOALL)
-	$(CC) -g -o qrexec_agent qrexec_agent.o exec.o txrx-vchan.o write_stdin.o buffer.o $(XENLIBS)
+	$(CC) -g -o qrexec_agent qrexec_agent.o exec.o txrx-vchan.o write_stdin.o buffer.o $(COMMONIOALL) $(XENLIBS)
 qrexec_client: qrexec_client.o $(COMMONIOALL) exec.o
 	$(CC) -g -o qrexec_client qrexec_client.o $(COMMONIOALL) exec.o
 clean:

qrexec/glue.h

@@ -45,3 +45,4 @@ int flush_client_data(int fd, int clid, struct buffer *buffer);
 int write_stdin(int fd, int clid, char *data, int len,
 		struct buffer *buffer);
 void set_nonblock(int fd);
+int fork_and_flush_stdin(int fd, struct buffer *buffer);

qrexec/qrexec_agent.c

@@ -206,8 +206,11 @@ void remove_process(int clid, int status)
 	int i;
 	if (!client_info[clid].pid)
 		return;
+        fork_and_flush_stdin(client_info[clid].stdin_fd, &client_info[clid].buffer); 
+#if 0 
+//      let's let it die by itself, possibly after it has received buffered stdin
 	kill(client_info[clid].pid, SIGKILL);
-
+#endif
 	if (status != -1)
 		send_exit_code(clid, status);
 

qrexec/qrexec_daemon.c

@@ -118,10 +118,15 @@ void handle_new_client()
 		max_client_fd = fd;
 }
 
+int children_count;
+
 void flush_client(int fd)
 {
 	int i;
 	struct server_header s_hdr;
+	
+	if (fork_and_flush_stdin(fd, &clients[fd].buffer))
+	        children_count++;
 	close(fd);
 	clients[fd].state = CLIENT_INVALID;
 	buffer_free(&clients[fd].buffer);
@@ -249,7 +254,6 @@ void pass_to_client(int clid, struct client_header *hdr)
 	}
 }
 
-int children_count;
 int child_exited;
 
 void sigchld_handler(int x)

qrexec/write_stdin.c

@@ -23,6 +23,8 @@
 #include <unistd.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <ioall.h>
+#include <stdlib.h>
 #include "qrexec.h"
 #include "buffer.h"
 #include "glue.h"
@@ -66,7 +68,7 @@ int write_stdin(int fd, int clid, char *data, int len,
 		buffer_append(buffer, data, len);
 		return WRITE_STDIN_BUFFERED;
 	}
-	
+
 	ret = write(fd, data, len);
 	if (ret == len)
 		return WRITE_STDIN_OK;
@@ -96,3 +98,31 @@ void set_nonblock(int fd)
 	int fl = fcntl(fd, F_GETFL, 0);
 	fcntl(fd, F_SETFL, fl | O_NONBLOCK);
 }
+
+void set_block(int fd)
+{
+	int fl = fcntl(fd, F_GETFL, 0);
+	fcntl(fd, F_SETFL, fl & ~O_NONBLOCK);
+}
+
+int fork_and_flush_stdin(int fd, struct buffer *buffer)
+{
+	int i;
+	if (!buffer_len(buffer))
+		return 0;
+	switch (fork()) {
+	case -1:
+		perror("fork");
+		exit(1);
+	case 0:
+		break;
+	default:
+		return 1;
+	}
+	for (i = 0; i < MAX_FDS; i++)
+		if (i != fd && i != 2)
+			close(i);
+	set_block(fd);
+	write_all(fd, buffer_data(buffer), buffer_len(buffer));
+	exit(0);
+}