[CRIU] [PATCHv3 7/8] remote: Use tmp file buffer when restore ip dump

[Radostin Stoyanov]

When CRIU calls the ip tool on restore, it passes the fd of remote
socket by replacing the STDIN before execvp. The stdin is used by the
ip tool to receive input. However, the ip tool calls ftell(stdin)
which fails with "Illegal seek" since UNIX sockets do not support file
positioning operations. To resolve this issue, read the received
content from the UNIX socket and store it into temporary file, then
replace STDIN with the fd of this tmp file.

Fixes #311

Signed-off-by: Radostin Stoyanov <rstoyanov1 at gmail.com>
---
 criu/net.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/criu/net.c b/criu/net.c
index 0431b62f..679212d0 100644
--- a/criu/net.c
+++ b/criu/net.c
@@ -1914,19 +1914,27 @@ out:
 
 static int restore_ip_dump(int type, int pid, char *cmd)
 {
-	int ret = -1;
+	int ret = -1, sockfd, n;
+	FILE *tmp_file;
 	struct cr_img *img;
+	char buf[1024];
 
 	img = open_image(type, O_RSTR, pid);
 	if (empty_image(img)) {
 		close_image(img);
 		return 0;
 	}
+	sockfd = img_raw_fd(img);
+	tmp_file = tmpfile();
+	while ((n = read(sockfd, buf, 1024)) > 0)
+		fwrite(buf, sizeof(char), n, tmp_file);
+	fseek(tmp_file, 0, SEEK_SET);
+
 	if (img) {
-		ret = run_ip_tool(cmd, "restore", NULL, NULL, img_raw_fd(img), -1, 0);
+		ret = run_ip_tool(cmd, "restore", NULL, NULL, fileno(tmp_file), -1, 0);
 		close_image(img);
 	}
-
+	fclose(tmp_file);
 	return ret;
 }
 
-- 
2.17.1