[Libguestfs] [PATCH] p2v: avoid connecting to ourself while probing qemu-nbd (RHBZ#1167774)

--- p2v/conversion.c | 43 +++++++++++++++++++++++++++++++++++++------ 1 file changed, 37 insertions(+), 6 deletions(-) diff --git a/p2v/conversion.c b/p2v/conversion.c index 4ff7ecc..14e7b3b 100644 --- a/p2v/conversion.c +++ b/p2v/conversion.c @@ -398,7 +398,8 @@ wait_qemu_nbd (int nbd_local_port, int timeout_seconds) { int sockfd; int result = -1; - struct sockaddr_in addr; + int reuseaddr = 1; + 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 +414,40 @@ 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; + /* Source port for probing qemu-nbd should be one greater than + * nbd_local_port. It's not guaranteed to always bind to this port, + * but it will hint the kernel to start there and try incrementally + * higher ports if needed. This avoids the case where the kernel + * selects nbd_local_port as our source port, and we immediately + * connect to ourself. See: + * https://bugzilla.redhat.com/show_bug.cgi?id=1167774#c9 + */ + src_addr.sin_port = htons (nbd_local_port+1); + 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 we run p2v repeatedly (say, running the tests in a loop), + * there's a decent chance we'll end up trying to bind() to a port + * that is in TIME_WAIT from a prior run. Handle that gracefully + * with SO_REUSEADDR. + */ + if (setsockopt (sockfd, SOL_SOCKET, SO_REUSEADDR, + &reuseaddr, sizeof reuseaddr) == -1) { + set_conversion_error ("waiting for qemu-nbd to start: setsockopt: %m"); + goto cleanup; + } + + if (bind (sockfd, (struct sockaddr *) &src_addr, sizeof src_addr) == -1) { + set_conversion_error ("waiting for qemu-nbd to start: bind(%d): %m", + ntohs (src_addr.sin_port)); + goto cleanup; + } for (;;) { time (&now_t); @@ -426,7 +457,7 @@ 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