epoll_ref contains a variety of information useful when handling epoll
events on our sockets, and we place it in the epoll_event data field
returned by epoll. However, for a few other things we use the 'fd' field
in the standard union of types for that data field.
This actually introduces a bug which is vanishingly unlikely to hit in
practice, but very nasty if it ever did: theoretically if we had a very
large file descriptor number for fd_tap or fd_tap_listen it could overflow
into bits that overlap with the 'proto' field in epoll_ref. With some
very bad luck this could mean that we mistakenly think an event on a
regular socket is an event on fd_tap or fd_tap_listen.
More practically, using different (but overlapping) fields of the
epoll_data means we can't unify dispatch for the various different objects
in the epoll. Therefore use the same epoll_ref as the data for the tap
fds and the netns quit fd, adding new fd type values to describe them.
Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
passt.c | 11 ++++++-----
passt.h | 6 +++++-
pasta.c | 8 ++++++--
tap.c | 16 ++++++++++++----
4 files changed, 29 insertions(+), 12 deletions(-)
diff --git a/passt.c b/passt.c
index b42f42d..195fccf 100644
--- a/passt.c
+++ b/passt.c
@@ -60,6 +60,8 @@ char *epoll_type_str[EPOLL_TYPE_MAX+1] = {
[EPOLL_TYPE_UDP] = "UDP socket",
[EPOLL_TYPE_ICMP] = "ICMP socket",
[EPOLL_TYPE_ICMPV6] = "ICMPv6 socket",
+ [EPOLL_TYPE_NSQUIT] = "namespace inotify",
+ [EPOLL_TYPE_TAP] = "tap device",
};
/**
@@ -328,12 +330,11 @@ loop:
for (i = 0; i < nfds; i++) {
union epoll_ref ref = *((union epoll_ref *)&events[i].data.u64);
- int fd = events[i].data.fd;
- if (fd == c.fd_tap || fd == c.fd_tap_listen)
- tap_handler(&c, fd, events[i].events, &now);
- else if (fd == quit_fd)
- pasta_netns_quit_handler(&c, fd);
+ if (ref.type == EPOLL_TYPE_TAP)
+ tap_handler(&c, ref.fd, events[i].events, &now);
+ else if (ref.type == EPOLL_TYPE_NSQUIT)
+ pasta_netns_quit_handler(&c, quit_fd);
else
sock_handler(&c, ref, events[i].events, &now);
}
diff --git a/passt.h b/passt.h
index 2110781..8878a11 100644
--- a/passt.h
+++ b/passt.h
@@ -55,8 +55,12 @@ enum epoll_type {
EPOLL_TYPE_ICMP,
/* ICMPv6 sockets */
EPOLL_TYPE_ICMPV6,
+ /* inotify fd watching for end of netns (pasta) */
+ EPOLL_TYPE_NSQUIT,
+ /* tap char device, or qemu socket fd */
+ EPOLL_TYPE_TAP,
- EPOLL_TYPE_MAX = EPOLL_TYPE_ICMPV6,
+ EPOLL_TYPE_MAX = EPOLL_TYPE_TAP,
};
/**
diff --git a/pasta.c b/pasta.c
index 1e84680..dbe8e8c 100644
--- a/pasta.c
+++ b/pasta.c
@@ -365,7 +365,10 @@ void pasta_ns_conf(struct ctx *c)
int pasta_netns_quit_init(struct ctx *c)
{
int flags = O_NONBLOCK | O_CLOEXEC;
- struct epoll_event ev = { .events = EPOLLIN };
+ union epoll_ref ref = { .type = EPOLL_TYPE_NSQUIT };
+ struct epoll_event ev = {
+ .events = EPOLLIN
+ };
int inotify_fd;
if (c->mode != MODE_PASTA || c->no_netns_quit || !*c->netns_base)
@@ -381,7 +384,8 @@ int pasta_netns_quit_init(struct ctx *c)
return -1;
}
- ev.data.fd = inotify_fd;
+ ref.fd = inotify_fd;
+ ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, inotify_fd, &ev);
return inotify_fd;
diff --git a/tap.c b/tap.c
index c33c6c7..ad0decf 100644
--- a/tap.c
+++ b/tap.c
@@ -1076,6 +1076,7 @@ restart:
static void tap_sock_unix_init(struct ctx *c)
{
int fd = socket(AF_UNIX, SOCK_STREAM, 0);
+ union epoll_ref ref = { .type = EPOLL_TYPE_TAP };
struct epoll_event ev = { 0 };
struct sockaddr_un addr = {
.sun_family = AF_UNIX,
@@ -1128,8 +1129,9 @@ static void tap_sock_unix_init(struct ctx *c)
listen(fd, 0);
- ev.data.fd = c->fd_tap_listen = fd;
+ ref.fd = c->fd_tap_listen = fd;
ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
+ ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap_listen, &ev);
info("You can now start qemu (>= 7.2, with commit 13c6be96618c):");
@@ -1145,6 +1147,7 @@ static void tap_sock_unix_init(struct ctx *c)
*/
static void tap_sock_unix_new(struct ctx *c)
{
+ union epoll_ref ref = { .type = EPOLL_TYPE_TAP };
struct epoll_event ev = { 0 };
int v = INT_MAX / 2;
struct ucred ucred;
@@ -1181,8 +1184,9 @@ static void tap_sock_unix_new(struct ctx *c)
setsockopt(c->fd_tap, SOL_SOCKET, SO_SNDBUF, &v, sizeof(v)))
trace("tap: failed to set SO_SNDBUF to %i", v);
- ev.data.fd = c->fd_tap;
+ ref.fd = c->fd_tap;
ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
+ ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap, &ev);
}
@@ -1227,6 +1231,7 @@ static int tap_ns_tun(void *arg)
*/
static void tap_sock_tun_init(struct ctx *c)
{
+ union epoll_ref ref = { .type = EPOLL_TYPE_TAP };
struct epoll_event ev = { 0 };
NS_CALL(tap_ns_tun, c);
@@ -1235,8 +1240,9 @@ static void tap_sock_tun_init(struct ctx *c)
pasta_ns_conf(c);
- ev.data.fd = c->fd_tap;
+ ref.fd = c->fd_tap;
ev.events = EPOLLIN | EPOLLRDHUP;
+ ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap, &ev);
}
@@ -1258,11 +1264,13 @@ void tap_sock_init(struct ctx *c)
}
if (c->fd_tap != -1) { /* Passed as --fd */
+ union epoll_ref ref = { .type = EPOLL_TYPE_TAP };
struct epoll_event ev = { 0 };
ASSERT(c->one_off);
- ev.data.fd = c->fd_tap;
+ ref.fd = c->fd_tap;
ev.events = EPOLLIN | EPOLLET | EPOLLRDHUP;
+ ev.data.u64 = ref.u64;
epoll_ctl(c->epollfd, EPOLL_CTL_ADD, c->fd_tap, &ev);
return;
}
--
2.41.0