From 6693d18ae0232da2c6febc0decf099e4fd064381 Mon Sep 17 00:00:00 2001 From: Denys Fedoryshchenko Date: Sat, 8 Aug 2026 17:47:49 +0300 Subject: ipoe: flush sessions left by a previous instance with a single command On startup accel-pppd is expected to drop everything a previous instance left behind in the kernel. For sessions it did so by dumping them with IPOE_CMD_GET and sending one IPOE_CMD_DELETE per ifindex. That dump was written for the session backup code removed in 1972a7e5c and was never adapted to its new, destructive role: - it was issued on the socket subscribed to the packet multicast group, so it competed with the notifications that the still attached stale rx handlers keep generating; on a loaded box the receive buffer overruns and rtnl_dump_filter() gives up with ENOBUFS, - its return value was discarded, so such a failure was silent, - it ran before the interfaces were detached, which is what produces those notifications in the first place, - it was skipped entirely when the multicast group could not be resolved, again with nothing but a warning about packet handling, - and every session cost a socket, a round trip, a grace period and a full unregister_netdev(). Whatever it missed stays in the kernel forever: the daemon has no record of those sessions, so nothing ever deletes them, and every subscriber later assigned one of their addresses is refused with EEXIST by IPOE_CMD_MODIFY. Add IPOE_CMD_FLUSH, which unlinks all sessions in one go, waits for a single grace period and unregisters the devices with unregister_netdevice_many(), and use it instead. The old path is kept as a fallback for a module predating the command, which is reported as EOPNOTSUPP, and now checks its return value and uses a private socket. Reorder init() so the interfaces are detached before the multicast group is joined, and so the flush also runs when only the group lookup failed. --- accel-pppd/ctrl/ipoe/ipoe.h | 3 +- accel-pppd/ctrl/ipoe/ipoe_netlink.c | 101 +++++++++++++++++++++++++++++++----- 2 files changed, 91 insertions(+), 13 deletions(-) (limited to 'accel-pppd/ctrl') diff --git a/accel-pppd/ctrl/ipoe/ipoe.h b/accel-pppd/ctrl/ipoe/ipoe.h index 37c26a63..2bd3a14f 100644 --- a/accel-pppd/ctrl/ipoe/ipoe.h +++ b/accel-pppd/ctrl/ipoe/ipoe.h @@ -164,7 +164,8 @@ void ipoe_nl_delete_interfaces(void); int ipoe_nl_create(); void ipoe_nl_delete(int ifindex); int ipoe_nl_modify(int ifindex, uint32_t peer_addr, uint32_t addr, uint32_t gw, int link_ifindex, uint8_t *hwaddr); -void ipoe_nl_get_sessions(struct list_head *list); +int ipoe_nl_get_sessions(struct list_head *list); +int ipoe_nl_flush_sessions(void); int ipoe_nl_add_exclude(uint32_t addr, int mask); void ipoe_nl_del_exclude(uint32_t addr); int ipoe_nl_add_net(uint32_t addr, int mask); diff --git a/accel-pppd/ctrl/ipoe/ipoe_netlink.c b/accel-pppd/ctrl/ipoe/ipoe_netlink.c index 94b7f42a..6eee2dca 100644 --- a/accel-pppd/ctrl/ipoe/ipoe_netlink.c +++ b/accel-pppd/ctrl/ipoe/ipoe_netlink.c @@ -410,17 +410,23 @@ static int dump_session(const struct sockaddr_nl *addr, struct nlmsghdr *n, void return 0; } -void ipoe_nl_get_sessions(struct list_head *list) +int ipoe_nl_get_sessions(struct list_head *list) { + struct rtnl_handle rth; struct nlmsghdr *nlh; struct genlmsghdr *ghdr; struct { struct nlmsghdr n; char buf[1024]; } req; + int ret; - if (rth.fd == -1) - return; + /* a private socket, so that the dump does not have to compete with + * the packet notifications delivered to the multicast one */ + if (rtnl_open_byproto(&rth, 0, NETLINK_GENERIC)) { + log_error("ipoe: cannot open generic netlink socket\n"); + return -1; + } memset(&req, 0, sizeof(req)); @@ -434,11 +440,51 @@ void ipoe_nl_get_sessions(struct list_head *list) ghdr->cmd = IPOE_CMD_GET; if (rtnl_send(&rth, (char *)nlh, nlh->nlmsg_len) < 0) { - log_emerg("ipoe: failed to send dump request: %s\n", strerror(errno)); - return; + log_error("ipoe: failed to send dump request: %s\n", strerror(errno)); + rtnl_close(&rth); + return -1; + } + + ret = rtnl_dump_filter(&rth, dump_session, list, NULL, NULL); + + rtnl_close(&rth); + + return ret; +} + +int ipoe_nl_flush_sessions(void) +{ + struct rtnl_handle rth; + struct nlmsghdr *nlh; + struct genlmsghdr *ghdr; + struct { + struct nlmsghdr n; + char buf[128]; + } req; + int ret = 0; + + if (rtnl_open_byproto(&rth, 0, NETLINK_GENERIC)) { + log_error("ipoe: cannot open generic netlink socket\n"); + errno = EIO; + return -1; } - rtnl_dump_filter(&rth, dump_session, list, NULL, NULL); + memset(&req, 0, sizeof(req)); + + nlh = &req.n; + nlh->nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN); + nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK; + nlh->nlmsg_type = ipoe_genl_id; + + ghdr = NLMSG_DATA(&req.n); + ghdr->cmd = IPOE_CMD_FLUSH; + + if (rtnl_talk(&rth, nlh, 0, 0, nlh, NULL, NULL, 0) < 0) + ret = -1; + + rtnl_close(&rth); + + return ret; } void ipoe_nl_delete(int ifindex) @@ -479,7 +525,10 @@ static void delete_sessions() struct ipoe_session_info *info; LIST_HEAD(ds_list); - ipoe_nl_get_sessions(&ds_list); + + if (ipoe_nl_get_sessions(&ds_list)) + log_error("ipoe: failed to enumerate sessions left by a previous" + " instance, some of them are not removed\n"); while (!list_empty(&ds_list)) { info = list_entry(ds_list.next, typeof(*info), entry); @@ -489,6 +538,22 @@ static void delete_sessions() } } +static void flush_sessions() +{ + if (!ipoe_nl_flush_sessions()) + return; + + if (errno == EOPNOTSUPP) { + log_warn("ipoe: loaded ipoe module does not support IPOE_CMD_FLUSH," + " removing sessions one by one, reload the module to fix\n"); + delete_sessions(); + return; + } + + log_error("ipoe: failed to remove sessions left by a previous instance:" + " %s\n", strerror(errno)); +} + static void ipoe_up_handler(const struct sockaddr_nl *addr, struct nlmsghdr *h) { struct rtattr *tb[PKT_ATTR_MAX + 1]; @@ -648,6 +713,23 @@ static void init(void) log_warn("failed to load ipoe module\n"); mcg_id = genl_resolve_mcg(IPOE_GENL_NAME, IPOE_GENL_MCG_PKT, &ipoe_genl_id); + + if (!ipoe_genl_id) { + log_error("ipoe: cannot resolve netlink family, state left by a" + " previous instance is not removed\n"); + rth.fd = -1; + return; + } + + /* Drop everything a previous instance may have left in the kernel. + * The interfaces go first: while their rx handlers are still attached + * the module keeps reporting unclassified packets, and once we join + * the multicast group that traffic competes with our own replies. */ + ipoe_nl_delete_interfaces(); + flush_sessions(); + ipoe_nl_del_exclude(0); + ipoe_nl_del_net(0); + if (mcg_id == -1) { log_warn("ipoe: unclassified packet handling is disabled\n"); rth.fd = -1; @@ -660,11 +742,6 @@ static void init(void) return; } - delete_sessions(); - ipoe_nl_del_exclude(0); - ipoe_nl_del_net(0); - ipoe_nl_delete_interfaces(); - fcntl(rth.fd, F_SETFL, O_NONBLOCK); fcntl(rth.fd, F_SETFD, fcntl(rth.fd, F_GETFD) | FD_CLOEXEC); -- cgit v1.2.3