mirror of https://gerrit.osmocom.org/libosmocore
ns2: Work around AF_PACKET socket ENOBUFS problems
AF_PACKET sockets cannot be written-to using select(), as they will always return "writable" but then still fail with ENOBUFS. This also means that we cannot use osmo_wqueue() as it assumes that a writable socket can actually be written to. As there's no way to figure out when exactly we can again perform a successful write, we have no other option but to start a timer and re-try at a later time. We will scale that timer based on the estimated duration of transmission for the just-failed PDU on the line rate of a 31TS E1 Line. Furthermore, with this patch, we stop queueing anything but signaling traffic (NS-BVCI=0) or Q.933 LMI. User data (NS-BVCI != 0) will instead be dropped in order to avoid buffer-bloat. Change-Id: I4f79a246236c94175ceffa5f3f556c8931c6bc62 Closes: OS#4995
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0b7614b408
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d06128d17d
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@ -4,7 +4,7 @@
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* 3GPP TS 08.16 version 8.0.1 Release 1999 / ETSI TS 101 299 V8.0.1 (2002-05)
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* as well as its successor 3GPP TS 48.016 */
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/* (C) 2009-2010,2014,2017 by Harald Welte <laforge@gnumonks.org>
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/* (C) 2009-2021 by Harald Welte <laforge@gnumonks.org>
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* (C) 2020 sysmocom - s.f.m.c. GmbH
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* Author: Alexander Couzens <lynxis@fe80.eu>
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*
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@ -51,9 +51,11 @@
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#include <osmocom/core/msgb.h>
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#include <osmocom/core/select.h>
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#include <osmocom/core/socket.h>
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#include <osmocom/core/timer.h>
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#include <osmocom/core/talloc.h>
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#include <osmocom/core/write_queue.h>
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#include <osmocom/gprs/gprs_ns2.h>
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#include <osmocom/gprs/protocol/gsm_08_16.h>
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#include <osmocom/gprs/protocol/gsm_08_18.h>
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#ifdef ENABLE_LIBMNL
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#include <osmocom/core/mnl.h>
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@ -72,6 +74,14 @@
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# define IPPROTO_GRE 47
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#endif
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#define E1_LINERATE 2048000
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#define E1_SLOTS_TOTAL 32
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#define E1_SLOTS_USED 31
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/* usable bitrate of the E1 superchannel with 31 of 32 timeslots */
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#define SUPERCHANNEL_LINERATE (E1_LINERATE*E1_SLOTS_USED)/E1_SLOTS_TOTAL
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/* nanoseconds per bit (504) */
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#define BIT_DURATION_NS (1000000000 / SUPERCHANNEL_LINERATE)
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struct gre_hdr {
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uint16_t flags;
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uint16_t ptype;
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@ -88,9 +98,19 @@ struct gprs_ns2_vc_driver vc_driver_fr = {
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struct priv_bind {
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char netif[IFNAMSIZ];
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struct osmo_fr_link *link;
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struct osmo_wqueue wqueue;
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int ifindex;
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bool if_running;
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/* backlog queue for AF_PACKET / ENOBUFS handling (see OS#4993) */
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struct {
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/* file-descriptor for AF_PACKET socket */
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struct osmo_fd ofd;
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/* list of msgb (backlog) */
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struct llist_head list;
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/* timer to trigger next attempt of AF_PACKET write */
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struct osmo_timer_list timer;
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/* re-try after that many micro-seconds */
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uint32_t retry_us;
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} backlog;
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};
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struct priv_vc {
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@ -138,6 +158,7 @@ static void dump_vty(const struct gprs_ns2_vc_bind *bind, struct vty *vty, bool
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static void free_bind(struct gprs_ns2_vc_bind *bind)
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{
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struct priv_bind *priv;
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struct msgb *msg, *msg2;
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OSMO_ASSERT(gprs_ns2_is_fr_bind(bind));
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if (!bind)
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@ -147,8 +168,13 @@ static void free_bind(struct gprs_ns2_vc_bind *bind)
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OSMO_ASSERT(llist_empty(&bind->nsvc));
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osmo_timer_del(&priv->backlog.timer);
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llist_for_each_entry_safe(msg, msg2, &priv->backlog.list, list) {
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msgb_free(msg);
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}
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osmo_fr_link_free(priv->link);
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osmo_fd_close(&priv->wqueue.bfd);
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osmo_fd_close(&priv->backlog.ofd);
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talloc_free(priv);
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}
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@ -200,15 +226,21 @@ int gprs_ns2_find_vc_by_dlci(struct gprs_ns2_vc_bind *bind,
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}
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/* PDU from the network interface towards the fr layer (upwards) */
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static int handle_netif_read(struct osmo_fd *bfd)
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static int fr_netif_ofd_cb(struct osmo_fd *bfd, uint32_t what)
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{
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struct gprs_ns2_vc_bind *bind = bfd->data;
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struct priv_bind *priv = bind->priv;
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struct msgb *msg = msgb_alloc(NS_ALLOC_SIZE, "Gb/NS/FR/GRE Rx");
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struct msgb *msg;
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struct sockaddr_ll sll;
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socklen_t sll_len = sizeof(sll);
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int rc = 0;
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/* we only handle read here. write to AF_PACKET sockets cannot be triggered
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* by select or poll, see OS#4995 */
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if (!(what & OSMO_FD_READ))
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return 0;
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msg = msgb_alloc(NS_ALLOC_SIZE, "Gb/NS/FR/GRE Rx");
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if (!msg)
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return -ENOMEM;
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@ -245,18 +277,35 @@ static int fr_dlci_rx_cb(void *cb_data, struct msgb *msg)
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return rc;
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}
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static int handle_netif_write(struct osmo_fd *ofd, struct msgb *msg)
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static int fr_netif_write_one(struct gprs_ns2_vc_bind *bind, struct msgb *msg)
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{
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struct gprs_ns2_vc_bind *bind = ofd->data;
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struct priv_bind *priv = bind->priv;
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unsigned int len = msgb_length(msg);
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int rc;
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rc = write(ofd->fd, msgb_data(msg), msgb_length(msg));
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/* write_queue expects a "-errno" type return value in case of failure */
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if (rc == -1) {
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LOGBIND(bind, LOGL_ERROR, "error during write to AF_PACKET: %s\n", strerror(errno));
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return -errno;
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} else
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return rc;
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/* estimate the retry time based on the data rate it takes to transmit */
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priv->backlog.retry_us = (BIT_DURATION_NS * 8 * len) / 1000;
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rc = write(priv->backlog.ofd.fd, msgb_data(msg), len);
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if (rc == len) {
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msgb_free(msg);
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return 0;
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} else if (rc < 0) {
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/* don't free, the caller might want to re-transmit */
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switch (errno) {
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case EAGAIN:
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case ENOBUFS:
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return -errno;
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default:
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LOGBIND(bind, LOGL_ERROR, "error during write to AF_PACKET: %s\n", strerror(errno));
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return -errno;
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}
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} else {
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/* short write */
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LOGBIND(bind, LOGL_ERROR, "short write on AF_PACKET: %d < %d\n", rc, len);
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msgb_free(msg);
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return 0;
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}
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}
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/*! determine if given bind is for FR-GRE encapsulation. */
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@ -274,16 +323,108 @@ static int fr_vc_sendmsg(struct gprs_ns2_vc *nsvc, struct msgb *msg)
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return osmo_fr_tx_dlc(msg);
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}
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static void enqueue_at_head(struct gprs_ns2_vc_bind *bind, struct msgb *msg)
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{
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struct priv_bind *priv = bind->priv;
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llist_add(&msg->list, &priv->backlog.list);
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osmo_timer_schedule(&priv->backlog.timer, 0, priv->backlog.retry_us);
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}
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static void enqueue_at_tail(struct gprs_ns2_vc_bind *bind, struct msgb *msg)
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{
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struct priv_bind *priv = bind->priv;
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llist_add_tail(&msg->list, &priv->backlog.list);
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osmo_timer_schedule(&priv->backlog.timer, 0, priv->backlog.retry_us);
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}
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#define LMI_Q933A_DLCI 0
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/* enqueue to backlog (LMI, signaling) or drop (userdata msg) */
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static void backlog_enqueue_or_free(struct gprs_ns2_vc_bind *bind, struct msgb *msg)
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{
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uint8_t dlci = msg->data[0];
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uint8_t ns_pdu_type;
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uint16_t bvci;
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if (msgb_length(msg) < 1)
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goto out_free;
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/* we want to enqueue only Q.933 LMI traffic or NS signaling; NOT user traffic */
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switch (dlci) {
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case LMI_Q933A_DLCI:
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/* enqueue Q.933 LMI at head of queue */
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enqueue_at_head(bind, msg);
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return;
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default:
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if (msgb_length(msg) < 3)
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break;
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ns_pdu_type = msg->data[2];
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switch (ns_pdu_type) {
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case NS_PDUT_UNITDATA:
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if (msgb_length(msg) < 6)
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break;
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bvci = osmo_load16be(msg->data + 4);
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/* enqueue BVCI=0 traffic at tail of queue */
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if (bvci == BVCI_SIGNALLING) {
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enqueue_at_tail(bind, msg);
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return;
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}
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break;
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default:
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/* enqueue NS signaling traffic at head of queue */
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enqueue_at_head(bind, msg);
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return;
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}
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break;
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}
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out_free:
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/* drop everything that is not LMI, NS-signaling or BVCI-0 */
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msgb_free(msg);
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}
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static void fr_backlog_timer_cb(void *data)
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{
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struct gprs_ns2_vc_bind *bind = data;
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struct priv_bind *priv = bind->priv;
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int i, rc;
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/* attempt to send up to 10 messages in every timer */
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for (i = 0; i < 10; i++) {
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struct msgb *msg = msgb_dequeue(&priv->backlog.list);
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if (!msg)
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break;
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rc = fr_netif_write_one(bind, msg);
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if (rc < 0) {
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/* re-add at head of list */
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llist_add(&msg->list, &priv->backlog.list);
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break;
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}
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}
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/* re-start timer if we still have data in the queue */
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if (!llist_empty(&priv->backlog.list))
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osmo_timer_schedule(&priv->backlog.timer, 0, priv->backlog.retry_us);
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}
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/* PDU from the frame relay layer towards the network interface (downwards) */
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int fr_tx_cb(void *data, struct msgb *msg)
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{
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struct gprs_ns2_vc_bind *bind = data;
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struct priv_bind *priv = bind->priv;
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int rc;
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if (osmo_wqueue_enqueue(&priv->wqueue, msg)) {
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LOGBIND(bind, LOGL_ERROR, "frame relay %s: failed to enqueue message\n", priv->netif);
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msgb_free(msg);
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return -EINVAL;
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if (llist_empty(&priv->backlog.list)) {
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/* attempt to transmit right now */
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rc = fr_netif_write_one(bind, msg);
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if (rc < 0) {
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/* enqueue to backlog in case it fails */
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backlog_enqueue_or_free(bind, msg);
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}
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} else {
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/* enqueue to backlog */
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backlog_enqueue_or_free(bind, msg);
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}
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return 0;
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@ -643,11 +784,11 @@ int gprs_ns2_fr_bind(struct gprs_ns2_inst *nsi,
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rc = open_socket(priv->ifindex, bind);
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if (rc < 0)
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goto err_fr;
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osmo_wqueue_init(&priv->wqueue, 10);
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priv->wqueue.write_cb = handle_netif_write;
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priv->wqueue.read_cb = handle_netif_read;
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osmo_fd_setup(&priv->wqueue.bfd, rc, OSMO_FD_READ, osmo_wqueue_bfd_cb, bind, 0);
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rc = osmo_fd_register(&priv->wqueue.bfd);
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INIT_LLIST_HEAD(&priv->backlog.list);
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priv->backlog.retry_us = 2500; /* start with some non-zero value; this corrsponds to 496 bytes */
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osmo_timer_setup(&priv->backlog.timer, fr_backlog_timer_cb, bind);
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osmo_fd_setup(&priv->backlog.ofd, rc, OSMO_FD_READ, fr_netif_ofd_cb, bind, 0);
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rc = osmo_fd_register(&priv->backlog.ofd);
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if (rc < 0)
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goto err_fd;
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@ -667,7 +808,7 @@ int gprs_ns2_fr_bind(struct gprs_ns2_inst *nsi,
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return rc;
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err_fd:
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close(priv->wqueue.bfd.fd);
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close(priv->backlog.ofd.fd);
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err_fr:
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osmo_fr_link_free(fr_link);
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err_priv:
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