From bb9558679ffaae062ea26ef97d2273b148e9c515 Mon Sep 17 00:00:00 2001 From: Peter Maydell Date: Sat, 11 Aug 2012 22:24:35 +0100 Subject: [PATCH] iov_send_recv(): Handle zero bytes case even if OS does not POSIX allows sendmsg() and recvmsg() to fail EMSGSIZE if passed a zero msg.msg_iovlen (in particular the MacOS X implementation will do this). Handle the case where iov_send_recv() is passed a zero byte count explicitly, to avoid accidentally depending on the OS to treat zero msg_iovlen as a no-op. Signed-off-by: Peter Maydell Acked-by: Michael Tokarev Signed-off-by: Stefan Hajnoczi --- iov.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/iov.c b/iov.c index b3330610bb..60705c73ab 100644 --- a/iov.c +++ b/iov.c @@ -146,6 +146,13 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, unsigned iov_cnt, { ssize_t ret; unsigned si, ei; /* start and end indexes */ + if (bytes == 0) { + /* Catch the do-nothing case early, as otherwise we will pass an + * empty iovec to sendmsg/recvmsg(), and not all implementations + * accept this. + */ + return 0; + } /* Find the start position, skipping `offset' bytes: * first, skip all full-sized vector elements, */