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authorHarald Welte <laforge@osmocom.org>2021-01-30 21:17:21 +0100
committerHarald Welte <laforge@osmocom.org>2021-01-31 12:34:36 +0100
commitd06128d17d61eb3e9812e10a09d4e97352de6b72 (patch)
tree3d448e7ca8a32c0d3a038d291725bad020ae477e /src
parent0b7614b408dcb27eaceecac8365ab34adcce0c4d (diff)
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
Diffstat (limited to 'src')
-rw-r--r--src/gb/gprs_ns2_fr.c191
1 files changed, 166 insertions, 25 deletions
diff --git a/src/gb/gprs_ns2_fr.c b/src/gb/gprs_ns2_fr.c
index 096e150a..4bd9ff11 100644
--- a/src/gb/gprs_ns2_fr.c
+++ b/src/gb/gprs_ns2_fr.c
@@ -4,7 +4,7 @@
* 3GPP TS 08.16 version 8.0.1 Release 1999 / ETSI TS 101 299 V8.0.1 (2002-05)
* as well as its successor 3GPP TS 48.016 */
-/* (C) 2009-2010,2014,2017 by Harald Welte <laforge@gnumonks.org>
+/* (C) 2009-2021 by Harald Welte <laforge@gnumonks.org>
* (C) 2020 sysmocom - s.f.m.c. GmbH
* Author: Alexander Couzens <lynxis@fe80.eu>
*
@@ -51,9 +51,11 @@
#include <osmocom/core/msgb.h>
#include <osmocom/core/select.h>
#include <osmocom/core/socket.h>
+#include <osmocom/core/timer.h>
#include <osmocom/core/talloc.h>
-#include <osmocom/core/write_queue.h>
#include <osmocom/gprs/gprs_ns2.h>
+#include <osmocom/gprs/protocol/gsm_08_16.h>
+#include <osmocom/gprs/protocol/gsm_08_18.h>
#ifdef ENABLE_LIBMNL
#include <osmocom/core/mnl.h>
@@ -72,6 +74,14 @@
# define IPPROTO_GRE 47
#endif
+#define E1_LINERATE 2048000
+#define E1_SLOTS_TOTAL 32
+#define E1_SLOTS_USED 31
+/* usable bitrate of the E1 superchannel with 31 of 32 timeslots */
+#define SUPERCHANNEL_LINERATE (E1_LINERATE*E1_SLOTS_USED)/E1_SLOTS_TOTAL
+/* nanoseconds per bit (504) */
+#define BIT_DURATION_NS (1000000000 / SUPERCHANNEL_LINERATE)
+
struct gre_hdr {
uint16_t flags;
uint16_t ptype;
@@ -88,9 +98,19 @@ struct gprs_ns2_vc_driver vc_driver_fr = {
struct priv_bind {
char netif[IFNAMSIZ];
struct osmo_fr_link *link;
- struct osmo_wqueue wqueue;
int ifindex;
bool if_running;
+ /* backlog queue for AF_PACKET / ENOBUFS handling (see OS#4993) */
+ struct {
+ /* file-descriptor for AF_PACKET socket */
+ struct osmo_fd ofd;
+ /* list of msgb (backlog) */
+ struct llist_head list;
+ /* timer to trigger next attempt of AF_PACKET write */
+ struct osmo_timer_list timer;
+ /* re-try after that many micro-seconds */
+ uint32_t retry_us;
+ } backlog;
};
struct priv_vc {
@@ -138,6 +158,7 @@ static void dump_vty(const struct gprs_ns2_vc_bind *bind, struct vty *vty, bool
static void free_bind(struct gprs_ns2_vc_bind *bind)
{
struct priv_bind *priv;
+ struct msgb *msg, *msg2;
OSMO_ASSERT(gprs_ns2_is_fr_bind(bind));
if (!bind)
@@ -147,8 +168,13 @@ static void free_bind(struct gprs_ns2_vc_bind *bind)
OSMO_ASSERT(llist_empty(&bind->nsvc));
+ osmo_timer_del(&priv->backlog.timer);
+ llist_for_each_entry_safe(msg, msg2, &priv->backlog.list, list) {
+ msgb_free(msg);
+ }
+
osmo_fr_link_free(priv->link);
- osmo_fd_close(&priv->wqueue.bfd);
+ osmo_fd_close(&priv->backlog.ofd);
talloc_free(priv);
}
@@ -200,15 +226,21 @@ int gprs_ns2_find_vc_by_dlci(struct gprs_ns2_vc_bind *bind,
}
/* PDU from the network interface towards the fr layer (upwards) */
-static int handle_netif_read(struct osmo_fd *bfd)
+static int fr_netif_ofd_cb(struct osmo_fd *bfd, uint32_t what)
{
struct gprs_ns2_vc_bind *bind = bfd->data;
struct priv_bind *priv = bind->priv;
- struct msgb *msg = msgb_alloc(NS_ALLOC_SIZE, "Gb/NS/FR/GRE Rx");
+ struct msgb *msg;
struct sockaddr_ll sll;
socklen_t sll_len = sizeof(sll);
int rc = 0;
+ /* we only handle read here. write to AF_PACKET sockets cannot be triggered
+ * by select or poll, see OS#4995 */
+ if (!(what & OSMO_FD_READ))
+ return 0;
+
+ msg = msgb_alloc(NS_ALLOC_SIZE, "Gb/NS/FR/GRE Rx");
if (!msg)
return -ENOMEM;
@@ -245,18 +277,35 @@ static int fr_dlci_rx_cb(void *cb_data, struct msgb *msg)
return rc;
}
-static int handle_netif_write(struct osmo_fd *ofd, struct msgb *msg)
+static int fr_netif_write_one(struct gprs_ns2_vc_bind *bind, struct msgb *msg)
{
- struct gprs_ns2_vc_bind *bind = ofd->data;
+ struct priv_bind *priv = bind->priv;
+ unsigned int len = msgb_length(msg);
int rc;
- rc = write(ofd->fd, msgb_data(msg), msgb_length(msg));
- /* write_queue expects a "-errno" type return value in case of failure */
- if (rc == -1) {
- LOGBIND(bind, LOGL_ERROR, "error during write to AF_PACKET: %s\n", strerror(errno));
- return -errno;
- } else
- return rc;
+ /* estimate the retry time based on the data rate it takes to transmit */
+ priv->backlog.retry_us = (BIT_DURATION_NS * 8 * len) / 1000;
+
+ rc = write(priv->backlog.ofd.fd, msgb_data(msg), len);
+ if (rc == len) {
+ msgb_free(msg);
+ return 0;
+ } else if (rc < 0) {
+ /* don't free, the caller might want to re-transmit */
+ switch (errno) {
+ case EAGAIN:
+ case ENOBUFS:
+ return -errno;
+ default:
+ LOGBIND(bind, LOGL_ERROR, "error during write to AF_PACKET: %s\n", strerror(errno));
+ return -errno;
+ }
+ } else {
+ /* short write */
+ LOGBIND(bind, LOGL_ERROR, "short write on AF_PACKET: %d < %d\n", rc, len);
+ msgb_free(msg);
+ return 0;
+ }
}
/*! determine if given bind is for FR-GRE encapsulation. */
@@ -274,16 +323,108 @@ static int fr_vc_sendmsg(struct gprs_ns2_vc *nsvc, struct msgb *msg)
return osmo_fr_tx_dlc(msg);
}
+static void enqueue_at_head(struct gprs_ns2_vc_bind *bind, struct msgb *msg)
+{
+ struct priv_bind *priv = bind->priv;
+ llist_add(&msg->list, &priv->backlog.list);
+ osmo_timer_schedule(&priv->backlog.timer, 0, priv->backlog.retry_us);
+}
+
+static void enqueue_at_tail(struct gprs_ns2_vc_bind *bind, struct msgb *msg)
+{
+ struct priv_bind *priv = bind->priv;
+ llist_add_tail(&msg->list, &priv->backlog.list);
+ osmo_timer_schedule(&priv->backlog.timer, 0, priv->backlog.retry_us);
+}
+
+#define LMI_Q933A_DLCI 0
+
+/* enqueue to backlog (LMI, signaling) or drop (userdata msg) */
+static void backlog_enqueue_or_free(struct gprs_ns2_vc_bind *bind, struct msgb *msg)
+{
+ uint8_t dlci = msg->data[0];
+ uint8_t ns_pdu_type;
+ uint16_t bvci;
+
+ if (msgb_length(msg) < 1)
+ goto out_free;
+
+ /* we want to enqueue only Q.933 LMI traffic or NS signaling; NOT user traffic */
+ switch (dlci) {
+ case LMI_Q933A_DLCI:
+ /* enqueue Q.933 LMI at head of queue */
+ enqueue_at_head(bind, msg);
+ return;
+ default:
+ if (msgb_length(msg) < 3)
+ break;
+ ns_pdu_type = msg->data[2];
+ switch (ns_pdu_type) {
+ case NS_PDUT_UNITDATA:
+ if (msgb_length(msg) < 6)
+ break;
+ bvci = osmo_load16be(msg->data + 4);
+ /* enqueue BVCI=0 traffic at tail of queue */
+ if (bvci == BVCI_SIGNALLING) {
+ enqueue_at_tail(bind, msg);
+ return;
+ }
+ break;
+ default:
+ /* enqueue NS signaling traffic at head of queue */
+ enqueue_at_head(bind, msg);
+ return;
+ }
+ break;
+ }
+
+out_free:
+ /* drop everything that is not LMI, NS-signaling or BVCI-0 */
+ msgb_free(msg);
+}
+
+static void fr_backlog_timer_cb(void *data)
+{
+ struct gprs_ns2_vc_bind *bind = data;
+ struct priv_bind *priv = bind->priv;
+ int i, rc;
+
+ /* attempt to send up to 10 messages in every timer */
+ for (i = 0; i < 10; i++) {
+ struct msgb *msg = msgb_dequeue(&priv->backlog.list);
+ if (!msg)
+ break;
+
+ rc = fr_netif_write_one(bind, msg);
+ if (rc < 0) {
+ /* re-add at head of list */
+ llist_add(&msg->list, &priv->backlog.list);
+ break;
+ }
+ }
+
+ /* re-start timer if we still have data in the queue */
+ if (!llist_empty(&priv->backlog.list))
+ osmo_timer_schedule(&priv->backlog.timer, 0, priv->backlog.retry_us);
+}
+
/* PDU from the frame relay layer towards the network interface (downwards) */
int fr_tx_cb(void *data, struct msgb *msg)
{
struct gprs_ns2_vc_bind *bind = data;
struct priv_bind *priv = bind->priv;
+ int rc;
- if (osmo_wqueue_enqueue(&priv->wqueue, msg)) {
- LOGBIND(bind, LOGL_ERROR, "frame relay %s: failed to enqueue message\n", priv->netif);
- msgb_free(msg);
- return -EINVAL;
+ if (llist_empty(&priv->backlog.list)) {
+ /* attempt to transmit right now */
+ rc = fr_netif_write_one(bind, msg);
+ if (rc < 0) {
+ /* enqueue to backlog in case it fails */
+ backlog_enqueue_or_free(bind, msg);
+ }
+ } else {
+ /* enqueue to backlog */
+ backlog_enqueue_or_free(bind, msg);
}
return 0;
@@ -643,11 +784,11 @@ int gprs_ns2_fr_bind(struct gprs_ns2_inst *nsi,
rc = open_socket(priv->ifindex, bind);
if (rc < 0)
goto err_fr;
- osmo_wqueue_init(&priv->wqueue, 10);
- priv->wqueue.write_cb = handle_netif_write;
- priv->wqueue.read_cb = handle_netif_read;
- osmo_fd_setup(&priv->wqueue.bfd, rc, OSMO_FD_READ, osmo_wqueue_bfd_cb, bind, 0);
- rc = osmo_fd_register(&priv->wqueue.bfd);
+ INIT_LLIST_HEAD(&priv->backlog.list);
+ priv->backlog.retry_us = 2500; /* start with some non-zero value; this corrsponds to 496 bytes */
+ osmo_timer_setup(&priv->backlog.timer, fr_backlog_timer_cb, bind);
+ osmo_fd_setup(&priv->backlog.ofd, rc, OSMO_FD_READ, fr_netif_ofd_cb, bind, 0);
+ rc = osmo_fd_register(&priv->backlog.ofd);
if (rc < 0)
goto err_fd;
@@ -667,7 +808,7 @@ int gprs_ns2_fr_bind(struct gprs_ns2_inst *nsi,
return rc;
err_fd:
- close(priv->wqueue.bfd.fd);
+ close(priv->backlog.ofd.fd);
err_fr:
osmo_fr_link_free(fr_link);
err_priv: