From 548e05f76aad0580952714c0522e8fe3b9203ad5 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Fri, 11 Aug 2023 15:12:18 +1000 Subject: [PATCH] tap: Clean up behaviour for errors on listening Unix socket We call tap_sock_unix_new() to handle a new connection to the qemu socket if we get an EPOLLIN event on c->fd_tap_listen. If we get any other event on the fd, we'll fall through to the "tap reset" path. But that won't do anything relevant to the listening socket, it will just close the already connected socket. Furthermore, the only other event we're subscribed to for the listening socket is EPOLLRDHUP, which doesn't apply to a non connected socket. Remove EPOLLRDHUP from the subscribed events. We don't need to explicitly add EPOLLERR, because errors are always reported. There's no obvious case that would cause an error on a listening socket anyway, and it's not obvious how we'd recover, treat it as a fatal error if it ever does happen. Finally, fold all this handling into the tap_sock_unix_new() function, there's no real reason to split it between there and tap_handler(). Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- tap.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) diff --git a/tap.c b/tap.c index 279440b..fb7f543 100644 --- a/tap.c +++ b/tap.c @@ -1108,7 +1108,7 @@ static void tap_sock_unix_init(struct ctx *c) listen(fd, 0); ev.data.fd = c->fd_tap_listen = fd; - ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP; + ev.events = EPOLLIN | EPOLLET; epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap_listen, &ev); info("You can now start qemu (>= 7.2, with commit 13c6be96618c):"); @@ -1121,14 +1121,18 @@ static void tap_sock_unix_init(struct ctx *c) /** * tap_sock_unix_new() - Handle new connection on listening socket * @c: Execution context + * @events: epoll events */ -static void tap_sock_unix_new(struct ctx *c) +static void tap_sock_unix_new(struct ctx *c, uint32_t events) { struct epoll_event ev = { 0 }; int v = INT_MAX / 2; struct ucred ucred; socklen_t len; + if (events != EPOLLIN) + die("Error on listening Unix socket, exiting"); + len = sizeof(ucred); /* Another client is already connected: accept and close right away. */ @@ -1284,8 +1288,8 @@ static void tap_sock_reset(struct ctx *c) void tap_handler(struct ctx *c, int fd, uint32_t events, const struct timespec *now) { - if (fd == c->fd_tap_listen && events == EPOLLIN) { - tap_sock_unix_new(c); + if (fd == c->fd_tap_listen) { + tap_sock_unix_new(c, events); return; }