[Libguestfs] [PATCH] p2v: avoid connecting to ourself while probing qemu-nbd (RHBZ#1167774)
---
p2v/conversion.c | 32 ++++++++++++++++++++++++++------
1 file changed, 26 insertions(+), 6 deletions(-)
diff --git a/p2v/conversion.c b/p2v/conversion.c
index 4ff7ecc..5c0c78e 100644
--- a/p2v/conversion.c
+++ b/p2v/conversion.c
@@ -44,6 +44,16 @@
/* How long to wait for qemu-nbd to start (seconds). */
#define WAIT_QEMU_NBD_TIMEOUT 10
+/* Source port for probing qemu-nbd. Should be one greater than
+ * nbd_local_port in ssh.c (50123). It's not guaranteed to always
+ * bind to 50124, but it will hint the kernel to start there and try
+ * incrementally higher ports if needed. This avoids the case where
+ * the kernel selects 50123 as our source port, and we immediately
+ * connect to ourself.
+ * See: https://bugzilla.redhat.com/show_bug.cgi?id=1167774#c9
+ */
+static int nbd_probe_port = 50124;
+
/* Data per NBD connection / physical disk. */
struct data_conn {
mexp_h *h; /* miniexpect handle to ssh */
@@ -398,7 +408,7 @@ wait_qemu_nbd (int nbd_local_port, int timeout_seconds)
{
int sockfd;
int result = -1;
- struct sockaddr_in addr;
+ struct sockaddr_in src_addr, dst_addr;
time_t start_t, now_t;
struct timeval timeout = { .tv_usec = 0 };
char magic[8]; /* NBDMAGIC */
@@ -413,10 +423,20 @@ wait_qemu_nbd (int nbd_local_port, int timeout_seconds)
return -1;
}
- memset (&addr, 0, sizeof addr);
- addr.sin_family = AF_INET;
- addr.sin_port = htons (nbd_local_port);
- inet_pton (AF_INET, "localhost", &addr.sin_addr);
+ memset (&src_addr, 0, sizeof src_addr);
+ src_addr.sin_family = AF_INET;
+ src_addr.sin_port = htons (nbd_probe_port);
+ inet_pton (AF_INET, "localhost", &src_addr.sin_addr);
+
+ memset (&dst_addr, 0, sizeof dst_addr);
+ dst_addr.sin_family = AF_INET;
+ dst_addr.sin_port = htons (nbd_local_port);
+ inet_pton (AF_INET, "localhost", &dst_addr.sin_addr);
+
+ if (bind (sockfd, (struct sockaddr *) &src_addr, sizeof src_addr) == -1) {
+ perror ("bind");
+ return -1;
+ }
for (;;) {
time (&now_t);
@@ -426,7 +446,7 @@ wait_qemu_nbd (int nbd_local_port, int timeout_seconds)
goto cleanup;
}
- if (connect (sockfd, (struct sockaddr *) &addr, sizeof addr) == 0)
+ if (connect (sockfd, (struct sockaddr *) &dst_addr, sizeof dst_addr) == 0)
break;
}
--
2.1.0