The control message for exchange of pipe file descriptor should be received by recvmsg, and it might be eaten to stream file by qemu_recv() when receiving by two callbacks. So this patch adds unix_msgfd_lookup() to callback get_buffer as the only one receiver, where the pipe file descriptor would be caughted.
Signed-off-by: Lei Li <li...@linux.vnet.ibm.com> --- migration-local.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++-- 1 files changed, 65 insertions(+), 3 deletions(-) diff --git a/migration-local.c b/migration-local.c index e028beb..0f0896b 100644 --- a/migration-local.c +++ b/migration-local.c @@ -50,6 +50,8 @@ typedef struct QEMUFileLocal { bool unix_page_flipping; } QEMUFileLocal; +static bool pipefd_passed; + static int qemu_local_get_sockfd(void *opaque) { QEMUFileLocal *s = opaque; @@ -57,16 +59,76 @@ static int qemu_local_get_sockfd(void *opaque) return s->sockfd; } +static int unix_msgfd_lookup(void *opaque, struct msghdr *msg) +{ + QEMUFileLocal *s = opaque; + struct cmsghdr *cmsg; + bool found = false; + + for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) { + if (cmsg->cmsg_len != CMSG_LEN(sizeof(int)) || + cmsg->cmsg_level != SOL_SOCKET || + cmsg->cmsg_type != SCM_RIGHTS) + continue; + + /* PIPE file descriptor to be received */ + s->pipefd[0] = *((int *)CMSG_DATA(cmsg)); + } + + if (s->pipefd[0] <= 0) { + fprintf(stderr, "no pipe fd can be received\n"); + return found; + } + + DPRINTF("pipefd successfully received\n"); + return s->pipefd[0]; +} + static int qemu_local_get_buffer(void *opaque, uint8_t *buf, int64_t pos, int size) { QEMUFileLocal *s = opaque; ssize_t len; + struct msghdr msg = { NULL, }; + struct iovec iov[1]; + union { + struct cmsghdr cmsg; + char control[CMSG_SPACE(sizeof(int))]; + } msg_control; + + iov[0].iov_base = buf; + iov[0].iov_len = size; + + msg.msg_iov = iov; + msg.msg_iovlen = 1; + msg.msg_control = &msg_control; + msg.msg_controllen = sizeof(msg_control); for (;;) { - len = qemu_recv(s->sockfd, buf, size, 0); - if (len != -1) { - break; + if (!pipefd_passed) { + /* + * recvmsg is called here to catch the control message for + * the exchange of PIPE file descriptor until it is received. + */ + len = recvmsg(s->sockfd, &msg, 0); + if (len != -1) { + if (unix_msgfd_lookup(s, &msg) > 0) { + pipefd_passed = 1; + /* + * Do not count one byte taken by the PIPE file + * descriptor. + */ + len--; + } else { + len = -1; + } + break; + } + } else { + len = qemu_recv(s->sockfd, buf, size, 0); + if (len != -1) { + break; + } } if (socket_error() == EAGAIN) { -- 1.7.7.6