Skip to content

pcap-linux: fix EFD_NONBLOCK rejected in old kernel #1667

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
SmileyLemon wants to merge 1 commit into
base: libpcap-1.10
Choose a base branch
from
+48 −13
Open

pcap-linux: fix EFD_NONBLOCK rejected in old kernel #1667

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
61 changes: 48 additions & 13 deletions pcap-linux.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -232,6 +232,7 @@ static int pcap_setfilter_linux(pcap_t *, struct bpf_program *);
static int pcap_setdirection_linux(pcap_t *, pcap_direction_t);
static int pcap_set_datalink_linux(pcap_t *, int);
static void pcap_cleanup_linux(pcap_t *);
static int pcap_linux_open_breakloop_fd(pcap_t *);

union thdr {
struct tpacket2_hdr *h2;
Expand Down Expand Up @@ -384,6 +385,51 @@ pcapint_create_interface(const char *device, char *ebuf)
return handle;
}

/*
* Open the eventfd used to break out of blocking poll() calls.
*
* If eventfd isn't supported, continue without it; breakloop won't
* interrupt blocking poll(), but capture still works.
*/
static int
pcap_linux_open_breakloop_fd(pcap_t *handle)
{
struct pcap_linux *handlep = handle->priv;
int fd;
int flags;

fd = eventfd(0, EFD_NONBLOCK);
if (fd == -1 && errno == EINVAL) {
/*
* Some older kernels don't accept EFD_NONBLOCK in eventfd().
* Fall back to plain eventfd and set O_NONBLOCK via fcntl().
*/
fd = eventfd(0, 0);
if (fd != -1) {
flags = fcntl(fd, F_GETFL, 0);
if (flags == -1 || fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1) {
int save_errno = errno;
close(fd);
errno = save_errno;
fd = -1;
}
}
}

if (fd == -1) {
if (errno == ENOSYS || errno == EINVAL) {
handlep->poll_breakloop_fd = -1;
return 0;
}
pcapint_fmt_errmsg_for_errno(handle->errbuf,
PCAP_ERRBUF_SIZE, errno, "could not open eventfd");
return -1;
}
handlep->poll_breakloop_fd = fd;

return 0;
}

#ifdef HAVE_LIBNL
/*
* If interface {if_name} is a mac80211 driver, the file
Expand Down Expand Up @@ -1253,13 +1299,7 @@ pcap_activate_linux(pcap_t *handle)
* we're not going to start in non-blocking mode.
*/
if (!handle->opt.nonblock) {
handlep->poll_breakloop_fd = eventfd(0, EFD_NONBLOCK);
if (handlep->poll_breakloop_fd == -1) {
/*
* Failed.
*/
pcapint_fmt_errmsg_for_errno(handle->errbuf,
PCAP_ERRBUF_SIZE, errno, "could not open eventfd");
if (pcap_linux_open_breakloop_fd(handle) == -1) {
status = PCAP_ERROR;
goto fail;
}
Expand Down Expand Up @@ -3558,13 +3598,8 @@ pcap_setnonblock_linux(pcap_t *handle, int nonblock)
* We're setting the mode to blocking mode.
*/
if (handlep->poll_breakloop_fd == -1) {
/* If we did not have an eventfd, open one now that we are blocking. */
if ( ( handlep->poll_breakloop_fd = eventfd(0, EFD_NONBLOCK) ) == -1 ) {
pcapint_fmt_errmsg_for_errno(handle->errbuf,
PCAP_ERRBUF_SIZE, errno,
"could not open eventfd");
if (pcap_linux_open_breakloop_fd(handle) == -1)
return -1;
}
}
if (handlep->timeout < 0) {
handlep->timeout = ~handlep->timeout;
Expand Down