liblttng-ust/lttng-context-net-ns.c

   1 /*
   2  * SPDX-License-Identifier: LGPL-2.1-only
   3  *
   4  * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  * Copyright (C) 2019 Michael Jeanson <mjeanson@efficios.com>
   6  *
   7  * LTTng UST net namespace context.
   8  */
   9
  10 #define _LGPL_SOURCE
  11 #include <stddef.h>
  12 #include <sys/types.h>
  13 #include <sys/stat.h>
  14 #include <unistd.h>
  15 #include <lttng/ust-events.h>
  16 #include <lttng/ust-tracer.h>
  17 #include <lttng/ringbuffer-context.h>
  18 #include <ust-tid.h>
  19 #include <urcu/tls-compat.h>
  20
  21 #include "context-internal.h"
  22 #include "lttng-tracer-core.h"
  23 #include "ns.h"
  24
  25 /*
  26  * We cache the result to ensure we don't stat(2) the proc filesystem on
  27  * each event.
  28  */
  29 static DEFINE_URCU_TLS_INIT(ino_t, cached_net_ns, NS_INO_UNINITIALIZED);
  30
  31 static
  32 ino_t get_net_ns(void)
  33 {
  34         struct stat sb;
  35         ino_t net_ns;
  36
  37         net_ns = CMM_LOAD_SHARED(URCU_TLS(cached_net_ns));
  38
  39         /*
  40          * If the cache is populated, do nothing and return the
  41          * cached inode number.
  42          */
  43         if (caa_likely(net_ns != NS_INO_UNINITIALIZED))
  44                 return net_ns;
  45
  46         /*
  47          * At this point we have to populate the cache, set the initial
  48          * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode
  49          * number from the proc filesystem, this is the value we will
  50          * cache.
  51          */
  52         net_ns = NS_INO_UNAVAILABLE;
  53
  54         /*
  55          * /proc/thread-self was introduced in kernel v3.17
  56          */
  57         if (stat("/proc/thread-self/ns/net", &sb) == 0) {
  58                 net_ns = sb.st_ino;
  59         } else {
  60                 char proc_ns_path[LTTNG_PROC_NS_PATH_MAX];
  61
  62                 if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX,
  63                                 "/proc/self/task/%d/ns/net",
  64                                 lttng_gettid()) >= 0) {
  65
  66                         if (stat(proc_ns_path, &sb) == 0) {
  67                                 net_ns = sb.st_ino;
  68                         }
  69                 }
  70         }
  71
  72         /*
  73          * And finally, store the inode number in the cache.
  74          */
  75         CMM_STORE_SHARED(URCU_TLS(cached_net_ns), net_ns);
  76
  77         return net_ns;
  78 }
  79
  80 /*
  81  * The net namespace can change for 3 reasons
  82  *  * clone(2) called with CLONE_NEWNET
  83  *  * setns(2) called with the fd of a different net ns
  84  *  * unshare(2) called with CLONE_NEWNET
  85  */
  86 void lttng_context_net_ns_reset(void)
  87 {
  88         CMM_STORE_SHARED(URCU_TLS(cached_net_ns), NS_INO_UNINITIALIZED);
  89 }
  90
  91 static
  92 size_t net_ns_get_size(struct lttng_ust_ctx_field *field, size_t offset)
  93 {
  94         size_t size = 0;
  95
  96         size += lib_ring_buffer_align(offset, lttng_alignof(ino_t));
  97         size += sizeof(ino_t);
  98         return size;
  99 }
 100
 101 static
 102 void net_ns_record(struct lttng_ust_ctx_field *field,
 103                  struct lttng_ust_lib_ring_buffer_ctx *ctx,
 104                  struct lttng_ust_channel_buffer *chan)
 105 {
 106         ino_t net_ns;
 107
 108         net_ns = get_net_ns();
 109         lib_ring_buffer_align_ctx(ctx, lttng_alignof(net_ns));
 110         chan->ops->event_write(ctx, &net_ns, sizeof(net_ns));
 111 }
 112
 113 static
 114 void net_ns_get_value(struct lttng_ust_ctx_field *field,
 115                 struct lttng_ust_ctx_value *value)
 116 {
 117         value->u.s64 = get_net_ns();
 118 }
 119
 120 int lttng_add_net_ns_to_ctx(struct lttng_ust_ctx **ctx)
 121 {
 122         struct lttng_ust_ctx_field *field;
 123         struct lttng_ust_type_common *type;
 124         int ret;
 125
 126         type = lttng_ust_create_type_integer(sizeof(ino_t) * CHAR_BIT,
 127                         lttng_alignof(ino_t) * CHAR_BIT,
 128                         lttng_is_signed_type(ino_t),
 129                         BYTE_ORDER, 10);
 130         if (!type)
 131                 return -ENOMEM;
 132         field = lttng_append_context(ctx);
 133         if (!field) {
 134                 ret = -ENOMEM;
 135                 goto error_context;
 136         }
 137         if (lttng_find_context(*ctx, "net_ns")) {
 138                 ret = -EEXIST;
 139                 goto error_find_context;
 140         }
 141         field->event_field->name = strdup("net_ns");
 142         if (!field->event_field->name) {
 143                 ret = -ENOMEM;
 144                 goto error_name;
 145         }
 146         field->event_field->type = type;
 147         field->get_size = net_ns_get_size;
 148         field->record = net_ns_record;
 149         field->get_value = net_ns_get_value;
 150         lttng_context_update(*ctx);
 151         return 0;
 152
 153 error_name:
 154 error_find_context:
 155         lttng_remove_context_field(ctx, field);
 156 error_context:
 157         lttng_ust_destroy_type(type);
 158         return ret;
 159 }
 160
 161 /*
 162  *  * Force a read (imply TLS fixup for dlopen) of TLS variables.
 163  *   */
 164 void lttng_fixup_net_ns_tls(void)
 165 {
 166         asm volatile ("" : : "m" (URCU_TLS(cached_net_ns)));
 167 }