From: Ralf Lici Date: Fri, 28 Nov 2025 11:26:59 +0000 (+0100) Subject: dco: process messages immediately after read X-Git-Tag: v2.7_rc3~2 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7791f5358a5574d4ef1bd27e2d52300c9d98bd72;p=thirdparty%2Fopenvpn.git dco: process messages immediately after read Currently, reading and processing of incoming DCO messages are decoupled: notifications are read, parsed, and the relevant information is stored in fields of dco_context_t for later processing (with the only exception being stats). This approach is problematic on Linux, since libnl does not allow reading a single netlink message at a time, which can result in loss of information when multiple notifications are available. This change adopts a read -> parse -> process paradigm. On Linux, processing is now invoked directly from within the parsing callback, which libnl calls for each received netlink packet. The other interfaces are adapted accordingly to unify the processing model across all platforms. On Linux, however, a DEL_PEER notification from the kernel triggers a GET_PEER request from userspace, which clutters the netlink communication logic and can lead to errors or even process exit when multiple simultaneous DEL_PEER notifications are received. To avoid this, introduce a lock that prevents requesting stats while we are still busy parsing other messages. Reported-by: Stefan Baranoff Github: OpenVPN/openvpn#900 Github: OpenVPN/openvpn#918 Github: fixes OpenVPN/openvpn#919 Change-Id: Iefc251cb4483c0b9fb9d6a5207db4445cd884d52 Signed-off-by: Ralf Lici Acked-by: Gert Doering Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1403 Message-Id: <20251128112705.12613-1-gert@greenie.muc.de> URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg34785.html Signed-off-by: Gert Doering --- diff --git a/src/openvpn/dco.h b/src/openvpn/dco.h index e5e87093c..cd6e32aef 100644 --- a/src/openvpn/dco.h +++ b/src/openvpn/dco.h @@ -127,12 +127,13 @@ int open_tun_dco(struct tuntap *tt, openvpn_net_ctx_t *ctx, const char *dev); void close_tun_dco(struct tuntap *tt, openvpn_net_ctx_t *ctx); /** - * Read data from the DCO communication channel (i.e. a control packet) + * Read and process data from the DCO communication channel + * (i.e. a control packet) * * @param dco the DCO context * @return 0 on success or a negative error code otherwise */ -int dco_do_read(dco_context_t *dco); +int dco_read_and_process(dco_context_t *dco); /** * Install a DCO in the main event loop @@ -305,7 +306,7 @@ close_tun_dco(struct tuntap *tt, openvpn_net_ctx_t *ctx) } static inline int -dco_do_read(dco_context_t *dco) +dco_read_and_process(dco_context_t *dco) { ASSERT(false); return 0; diff --git a/src/openvpn/dco_freebsd.c b/src/openvpn/dco_freebsd.c index f2a89ac56..d1ad09212 100644 --- a/src/openvpn/dco_freebsd.c +++ b/src/openvpn/dco_freebsd.c @@ -578,7 +578,7 @@ dco_update_peer_stat(struct multi_context *m, uint32_t peerid, const nvlist_t *n } int -dco_do_read(dco_context_t *dco) +dco_read_and_process(dco_context_t *dco) { struct ifdrv drv; uint8_t buf[4096]; @@ -684,11 +684,21 @@ dco_do_read(dco_context_t *dco) default: msg(M_WARN, "%s: unknown kernel notification %d", __func__, type); + dco->dco_message_type = 0; break; } nvlist_destroy(nvl); + if (dco->c->mode == CM_TOP) + { + multi_process_incoming_dco(dco); + } + else + { + process_incoming_dco(dco); + } + return 0; } diff --git a/src/openvpn/dco_linux.c b/src/openvpn/dco_linux.c index 0ae30b185..266402994 100644 --- a/src/openvpn/dco_linux.c +++ b/src/openvpn/dco_linux.c @@ -49,6 +49,15 @@ #include #include +/* When parsing multiple DEL_PEER notifications, openvpn tries to request stats + * for each DEL_PEER message (see setenv_stats). This triggers a GET_PEER + * request-reply while we are still parsing the rest of the initial + * notifications, which can lead to NLE_BUSY or even NLE_NOMEM. + * + * This basic lock ensures we don't bite our own tail by issuing a dco_get_peer + * while still busy receiving and parsing other messages. + */ +static bool __is_locked = false; /* libnl < 3.5.0 does not set the NLA_F_NESTED on its own, therefore we * have to explicitly do it to prevent the kernel from failing upon @@ -127,7 +136,9 @@ nla_put_failure: static int ovpn_nl_recvmsgs(dco_context_t *dco, const char *prefix) { + __is_locked = true; int ret = nl_recvmsgs(dco->nl_sock, dco->nl_cb); + __is_locked = false; switch (ret) { @@ -1094,29 +1105,34 @@ ovpn_handle_msg(struct nl_msg *msg, void *arg) * message, that stores the type-specific attributes. * * the "dco" object is then filled accordingly with the information - * retrieved from the message, so that the rest of the OpenVPN code can - * react as need be. + * retrieved from the message, so that *process_incoming_dco can react + * as need be. */ + int ret; switch (gnlh->cmd) { case OVPN_CMD_PEER_GET: { + /* return directly, there are no messages to pass to *process_incoming_dco() */ return ovpn_handle_peer(dco, attrs); } case OVPN_CMD_PEER_DEL_NTF: { - return ovpn_handle_peer_del_ntf(dco, attrs); + ret = ovpn_handle_peer_del_ntf(dco, attrs); + break; } case OVPN_CMD_PEER_FLOAT_NTF: { - return ovpn_handle_peer_float_ntf(dco, attrs); + ret = ovpn_handle_peer_float_ntf(dco, attrs); + break; } case OVPN_CMD_KEY_SWAP_NTF: { - return ovpn_handle_key_swap_ntf(dco, attrs); + ret = ovpn_handle_key_swap_ntf(dco, attrs); + break; } default: @@ -1125,11 +1141,25 @@ ovpn_handle_msg(struct nl_msg *msg, void *arg) return NL_STOP; } + if (ret != NL_OK) + { + return ret; + } + + if (dco->c->mode == CM_TOP) + { + multi_process_incoming_dco(dco); + } + else + { + process_incoming_dco(dco); + } + return NL_OK; } int -dco_do_read(dco_context_t *dco) +dco_read_and_process(dco_context_t *dco) { msg(D_DCO_DEBUG, __func__); @@ -1141,6 +1171,12 @@ dco_get_peer(dco_context_t *dco, int peer_id, const bool raise_sigusr1_on_err) { ASSERT(dco); + if (__is_locked) + { + msg(D_DCO_DEBUG, "%s: cannot request peer stats while parsing other messages", __func__); + return 0; + } + /* peer_id == -1 means "dump all peers", but this is allowed in MP mode only. * If it happens in P2P mode it means that the DCO peer was deleted and we * can simply bail out diff --git a/src/openvpn/dco_win.c b/src/openvpn/dco_win.c index ca5eedfd6..94f043fe0 100644 --- a/src/openvpn/dco_win.c +++ b/src/openvpn/dco_win.c @@ -690,7 +690,7 @@ dco_handle_overlapped_success(dco_context_t *dco, bool queued) } int -dco_do_read(dco_context_t *dco) +dco_read_and_process(dco_context_t *dco) { if (dco->ifmode != DCO_MODE_MP) { @@ -727,6 +727,15 @@ dco_do_read(dco_context_t *dco) break; } + if (dco->c->mode == CM_TOP) + { + multi_process_incoming_dco(dco); + } + else + { + process_incoming_dco(dco); + } + return 0; } diff --git a/src/openvpn/forward.c b/src/openvpn/forward.c index bc600d6cd..6f1bc0cb1 100644 --- a/src/openvpn/forward.c +++ b/src/openvpn/forward.c @@ -1243,19 +1243,11 @@ extract_dco_float_peer_addr(const sa_family_t socket_family, struct openvpn_sock } } -static void -process_incoming_dco(struct context *c) +void +process_incoming_dco(dco_context_t *dco) { #if defined(ENABLE_DCO) && (defined(TARGET_LINUX) || defined(TARGET_FREEBSD)) - dco_context_t *dco = &c->c1.tuntap->dco; - - dco_do_read(dco); - - /* no message for us to handle - platform specific code has logged details */ - if (dco->dco_message_type == 0) - { - return; - } + struct context *c = dco->c; /* FreeBSD currently sends us removal notifcation with the old peer-id in * p2p mode with the ping timeout reason, so ignore that one to not shoot @@ -2369,7 +2361,7 @@ process_io(struct context *c, struct link_socket *sock) { if (!IS_SIG(c)) { - process_incoming_dco(c); + dco_read_and_process(&c->c1.tuntap->dco); } } } diff --git a/src/openvpn/forward.h b/src/openvpn/forward.h index 3cd710ed0..06808b93b 100644 --- a/src/openvpn/forward.h +++ b/src/openvpn/forward.h @@ -209,6 +209,13 @@ void process_incoming_link_part2(struct context *c, struct link_socket_info *lsi void extract_dco_float_peer_addr(sa_family_t socket_family, struct openvpn_sockaddr *out_osaddr, const struct sockaddr *float_sa); +/** + * Process an incoming DCO message (from kernel space). + * + * @param dco - Pointer to the structure representing the DCO context. + */ +void process_incoming_dco(dco_context_t *dco); + /** * Write a packet to the external network interface. * @ingroup external_multiplexer diff --git a/src/openvpn/multi.c b/src/openvpn/multi.c index 2b9446670..153695c49 100644 --- a/src/openvpn/multi.c +++ b/src/openvpn/multi.c @@ -3263,14 +3263,12 @@ process_incoming_del_peer(struct multi_context *m, struct multi_instance *mi, dc multi_signal_instance(m, mi, SIGTERM); } -bool -multi_process_incoming_dco(struct multi_context *m) +void +multi_process_incoming_dco(dco_context_t *dco) { - dco_context_t *dco = &m->top.c1.tuntap->dco; - - struct multi_instance *mi = NULL; + ASSERT(dco->c->multi); - int ret = dco_do_read(&m->top.c1.tuntap->dco); + struct multi_context *m = dco->c->multi; int peer_id = dco->dco_message_peer_id; @@ -3279,12 +3277,12 @@ multi_process_incoming_dco(struct multi_context *m) */ if (peer_id < 0) { - return ret > 0; + return; } if ((peer_id < m->max_clients) && (m->instances[peer_id])) { - mi = m->instances[peer_id]; + struct multi_instance *mi = m->instances[peer_id]; set_prefix(mi); if (dco->dco_message_type == OVPN_CMD_DEL_PEER) { @@ -3325,11 +3323,6 @@ multi_process_incoming_dco(struct multi_context *m) "type %d, del_peer_reason %d", peer_id, dco->dco_message_type, dco->dco_del_peer_reason); } - - dco->dco_message_type = 0; - dco->dco_message_peer_id = -1; - dco->dco_del_peer_reason = -1; - return ret > 0; } #endif /* if defined(ENABLE_DCO) */ @@ -4462,4 +4455,4 @@ multi_check_push_ifconfig_ipv6_extra_route(struct multi_instance *mi, return (!ipv6_net_contains_host(&ifconfig_local, o->ifconfig_ipv6_netbits, dest)); -} \ No newline at end of file +} diff --git a/src/openvpn/multi.h b/src/openvpn/multi.h index a62b07ae6..a44f9f25b 100644 --- a/src/openvpn/multi.h +++ b/src/openvpn/multi.h @@ -305,13 +305,9 @@ bool multi_process_post(struct multi_context *m, struct multi_instance *mi, /** * Process an incoming DCO message (from kernel space). * - * @param m - The single \c multi_context structure. - * - * @return - * - True, if the message was received correctly. - * - False, if there was an error while reading the message. + * @param dco - Pointer to the structure representing the DCO context. */ -bool multi_process_incoming_dco(struct multi_context *m); +void multi_process_incoming_dco(dco_context_t *dco); /**************************************************************************/ /** diff --git a/src/openvpn/multi_io.c b/src/openvpn/multi_io.c index fe7245615..997951ec0 100644 --- a/src/openvpn/multi_io.c +++ b/src/openvpn/multi_io.c @@ -505,7 +505,7 @@ multi_io_process_io(struct multi_context *m) /* incoming data on DCO? */ else if (e->arg == MULTI_IO_DCO) { - multi_process_incoming_dco(m); + dco_read_and_process(&m->top.c1.tuntap->dco); } #endif /* signal received? */