[dm-devel] [PATCH 17/35] libmultipath: remove uevent listener failback
mwilck at suse.com
mwilck at suse.com
Thu Jul 9 10:16:02 UTC 2020
From: Martin Wilck <mwilck at suse.com>
TL;DR: this code is obsolete.
The failback code uses the udev 'RUN+="socket:"' technique, which
has been deprecated since udev 178 and removed since udev 183,
in 2012. The corresponding udev rule in multipath-tools has been removed
in ad067ac ("multipath: do not install rules file"), in 0.5.0 (2013).
Since that time, the failback code has been non-functional and basically
unmaintained.
While there's yet another fallback to the netlink socket, this 2nd fallback
would only be used if the socket(AF_LOCAL, ...) call failed, which would be
very unlikely. Even with the AF_LOCAL failback removed, leaving this 2nd
fallback in place doesn't make sense because it's just a reimplementation
of udev_monitor_new_from_netlink(); it's hard to imagine a case where the
latter would fail but our code would succeed.
Signed-off-by: Martin Wilck <mwilck at suse.com>
---
libmultipath/uevent.c | 245 +-----------------------------------------
libmultipath/uevent.h | 4 -
2 files changed, 2 insertions(+), 247 deletions(-)
diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
index e0d13b1..6a3f8bd 100644
--- a/libmultipath/uevent.c
+++ b/libmultipath/uevent.c
@@ -450,243 +450,6 @@ int uevent_dispatch(int (*uev_trigger)(struct uevent *, void * trigger_data),
return 0;
}
-struct uevent *uevent_from_buffer(char *buf, ssize_t buflen)
-{
- struct uevent *uev;
- char *buffer;
- size_t bufpos;
- int i;
- char *pos;
-
- uev = alloc_uevent();
- if (!uev) {
- condlog(1, "lost uevent, oom");
- return NULL;
- }
-
- if ((size_t)buflen > sizeof(buf)-1)
- buflen = sizeof(buf)-1;
-
- /*
- * Copy the shared receive buffer contents to buffer private
- * to this uevent so we can immediately reuse the shared buffer.
- */
- memcpy(uev->buffer, buf, HOTPLUG_BUFFER_SIZE + OBJECT_SIZE);
- buffer = uev->buffer;
- buffer[buflen] = '\0';
-
- /* save start of payload */
- bufpos = strlen(buffer) + 1;
-
- /* action string */
- uev->action = buffer;
- pos = strchr(buffer, '@');
- if (!pos) {
- condlog(3, "bad action string '%s'", buffer);
- FREE(uev);
- return NULL;
- }
- pos[0] = '\0';
-
- /* sysfs path */
- uev->devpath = &pos[1];
-
- /* hotplug events have the environment attached - reconstruct envp[] */
- for (i = 0; (bufpos < (size_t)buflen) && (i < HOTPLUG_NUM_ENVP-1); i++) {
- int keylen;
- char *key;
-
- key = &buffer[bufpos];
- keylen = strlen(key);
- uev->envp[i] = key;
- /* Filter out sequence number */
- if (strncmp(key, "SEQNUM=", 7) == 0) {
- char *eptr;
-
- uev->seqnum = strtoul(key + 7, &eptr, 10);
- if (eptr == key + 7)
- uev->seqnum = -1;
- }
- bufpos += keylen + 1;
- }
- uev->envp[i] = NULL;
-
- condlog(3, "uevent %ld '%s' from '%s'", uev->seqnum,
- uev->action, uev->devpath);
- uev->kernel = strrchr(uev->devpath, '/');
- if (uev->kernel)
- uev->kernel++;
-
- /* print payload environment */
- for (i = 0; uev->envp[i] != NULL; i++)
- condlog(5, "%s", uev->envp[i]);
-
- return uev;
-}
-
-int failback_listen(void)
-{
- int sock;
- struct sockaddr_nl snl;
- struct sockaddr_un sun;
- socklen_t addrlen;
- int retval;
- int rcvbufsz = 128*1024;
- int rcvsz = 0;
- int rcvszsz = sizeof(rcvsz);
- unsigned int *prcvszsz = (unsigned int *)&rcvszsz;
- const int feature_on = 1;
- /*
- * First check whether we have a udev socket
- */
- memset(&sun, 0x00, sizeof(struct sockaddr_un));
- sun.sun_family = AF_LOCAL;
- strcpy(&sun.sun_path[1], "/org/kernel/dm/multipath_event");
- addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(sun.sun_path+1) + 1;
-
- sock = socket(AF_LOCAL, SOCK_DGRAM, 0);
- if (sock >= 0) {
-
- condlog(3, "reading events from udev socket.");
-
- /* the bind takes care of ensuring only one copy running */
- retval = bind(sock, (struct sockaddr *) &sun, addrlen);
- if (retval < 0) {
- condlog(0, "bind failed, exit");
- goto exit;
- }
-
- /* enable receiving of the sender credentials */
- retval = setsockopt(sock, SOL_SOCKET, SO_PASSCRED,
- &feature_on, sizeof(feature_on));
- if (retval < 0) {
- condlog(0, "failed to enable credential passing, exit");
- goto exit;
- }
-
- } else {
- /* Fallback to read kernel netlink events */
- memset(&snl, 0x00, sizeof(struct sockaddr_nl));
- snl.nl_family = AF_NETLINK;
- snl.nl_pid = getpid();
- snl.nl_groups = 0x01;
-
- sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
- if (sock == -1) {
- condlog(0, "error getting socket, exit");
- return 1;
- }
-
- condlog(3, "reading events from kernel.");
-
- /*
- * try to avoid dropping uevents, even so, this is not a guarantee,
- * but it does help to change the netlink uevent socket's
- * receive buffer threshold from the default value of 106,496 to
- * the maximum value of 262,142.
- */
- retval = setsockopt(sock, SOL_SOCKET, SO_RCVBUF, &rcvbufsz,
- sizeof(rcvbufsz));
-
- if (retval < 0) {
- condlog(0, "error setting receive buffer size for socket, exit");
- exit(1);
- }
- retval = getsockopt(sock, SOL_SOCKET, SO_RCVBUF, &rcvsz, prcvszsz);
- if (retval < 0) {
- condlog(0, "error setting receive buffer size for socket, exit");
- exit(1);
- }
- condlog(3, "receive buffer size for socket is %u.", rcvsz);
-
- /* enable receiving of the sender credentials */
- if (setsockopt(sock, SOL_SOCKET, SO_PASSCRED,
- &feature_on, sizeof(feature_on)) < 0) {
- condlog(0, "error on enabling credential passing for socket");
- exit(1);
- }
-
- retval = bind(sock, (struct sockaddr *) &snl,
- sizeof(struct sockaddr_nl));
- if (retval < 0) {
- condlog(0, "bind failed, exit");
- goto exit;
- }
- }
-
- while (1) {
- size_t bufpos;
- ssize_t buflen;
- struct uevent *uev;
- struct msghdr smsg;
- struct iovec iov;
- char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
- struct cmsghdr *cmsg;
- struct ucred *cred;
- static char buf[HOTPLUG_BUFFER_SIZE + OBJECT_SIZE];
-
- memset(buf, 0x00, sizeof(buf));
- iov.iov_base = &buf;
- iov.iov_len = sizeof(buf);
- memset (&smsg, 0x00, sizeof(struct msghdr));
- smsg.msg_iov = &iov;
- smsg.msg_iovlen = 1;
- smsg.msg_control = cred_msg;
- smsg.msg_controllen = sizeof(cred_msg);
-
- buflen = recvmsg(sock, &smsg, 0);
- if (buflen < 0) {
- if (errno != EINTR)
- condlog(0, "error receiving message, errno %d", errno);
- continue;
- }
-
- cmsg = CMSG_FIRSTHDR(&smsg);
- if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
- condlog(3, "no sender credentials received, message ignored");
- continue;
- }
-
- cred = (struct ucred *)CMSG_DATA(cmsg);
- if (cred->uid != 0) {
- condlog(3, "sender uid=%d, message ignored", cred->uid);
- continue;
- }
-
- /* skip header */
- bufpos = strlen(buf) + 1;
- if (bufpos < sizeof("a@/d") || bufpos >= sizeof(buf)) {
- condlog(3, "invalid message length");
- continue;
- }
-
- /* check message header */
- if (strstr(buf, "@/") == NULL) {
- condlog(3, "unrecognized message header");
- continue;
- }
- if ((size_t)buflen > sizeof(buf)-1) {
- condlog(2, "buffer overflow for received uevent");
- buflen = sizeof(buf)-1;
- }
-
- uev = uevent_from_buffer(buf, buflen);
- if (!uev)
- continue;
- /*
- * Queue uevent and poke service pthread.
- */
- pthread_mutex_lock(uevq_lockp);
- list_add_tail(&uev->node, &uevq);
- pthread_cond_signal(uev_condp);
- pthread_mutex_unlock(uevq_lockp);
- }
-
-exit:
- close(sock);
- return 1;
-}
-
struct uevent *uevent_from_udev_device(struct udev_device *dev)
{
struct uevent *uev;
@@ -786,7 +549,6 @@ int uevent_listen(struct udev *udev)
struct udev_monitor *monitor = NULL;
int fd, socket_flags, events;
struct timeval start_time;
- int need_failback = 1;
int timeout = 30;
LIST_HEAD(uevlisten_tmp);
@@ -806,7 +568,7 @@ int uevent_listen(struct udev *udev)
monitor = udev_monitor_new_from_netlink(udev, "udev");
if (!monitor) {
condlog(2, "failed to create udev monitor");
- goto failback;
+ goto out_udev;
}
pthread_cleanup_push(monitor_cleanup, monitor);
#ifdef LIBUDEV_API_RECVBUF
@@ -891,12 +653,9 @@ int uevent_listen(struct udev *udev)
gettimeofday(&start_time, NULL);
timeout = 30;
}
- need_failback = 0;
out:
pthread_cleanup_pop(1);
-failback:
- if (need_failback)
- err = failback_listen();
+out_udev:
pthread_cleanup_pop(1);
return err;
}
diff --git a/libmultipath/uevent.h b/libmultipath/uevent.h
index 0aa8675..4956bfc 100644
--- a/libmultipath/uevent.h
+++ b/libmultipath/uevent.h
@@ -9,10 +9,6 @@
#define HOTPLUG_NUM_ENVP 32
#define OBJECT_SIZE 512
-#ifndef NETLINK_KOBJECT_UEVENT
-#define NETLINK_KOBJECT_UEVENT 15
-#endif
-
struct udev;
struct uevent {
--
2.26.2
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