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 <limits.h>
  12 #include <stddef.h>
  13 #include <sys/types.h>
  14 #include <sys/stat.h>
  15 #include <unistd.h>
  16 #include <lttng/ust-events.h>
  17 #include <lttng/ust-tracer.h>
  18 #include <lttng/ringbuffer-context.h>
  19 #include <ust-tid.h>
  20 #include <urcu/tls-compat.h>
  21
  22 #include "context-internal.h"
  23 #include "lttng-tracer-core.h"
  24 #include "ns.h"
  25
  26 /*
  27  * We cache the result to ensure we don't stat(2) the proc filesystem on
  28  * each event.
  29  */
  30 static DEFINE_URCU_TLS_INIT(ino_t, cached_net_ns, NS_INO_UNINITIALIZED);
  31
  32 static
  33 ino_t get_net_ns(void)
  34 {
  35         struct stat sb;
  36         ino_t net_ns;
  37
  38         net_ns = CMM_LOAD_SHARED(URCU_TLS(cached_net_ns));
  39
  40         /*
  41          * If the cache is populated, do nothing and return the
  42          * cached inode number.
  43          */
  44         if (caa_likely(net_ns != NS_INO_UNINITIALIZED))
  45                 return net_ns;
  46
  47         /*
  48          * At this point we have to populate the cache, set the initial
  49          * value to NS_INO_UNAVAILABLE (0), if we fail to get the inode
  50          * number from the proc filesystem, this is the value we will
  51          * cache.
  52          */
  53         net_ns = NS_INO_UNAVAILABLE;
  54
  55         /*
  56          * /proc/thread-self was introduced in kernel v3.17
  57          */
  58         if (stat("/proc/thread-self/ns/net", &sb) == 0) {
  59                 net_ns = sb.st_ino;
  60         } else {
  61                 char proc_ns_path[LTTNG_PROC_NS_PATH_MAX];
  62
  63                 if (snprintf(proc_ns_path, LTTNG_PROC_NS_PATH_MAX,
  64                                 "/proc/self/task/%d/ns/net",
  65                                 lttng_gettid()) >= 0) {
  66
  67                         if (stat(proc_ns_path, &sb) == 0) {
  68                                 net_ns = sb.st_ino;
  69                         }
  70                 }
  71         }
  72
  73         /*
  74          * And finally, store the inode number in the cache.
  75          */
  76         CMM_STORE_SHARED(URCU_TLS(cached_net_ns), net_ns);
  77
  78         return net_ns;
  79 }
  80
  81 /*
  82  * The net namespace can change for 3 reasons
  83  *  * clone(2) called with CLONE_NEWNET
  84  *  * setns(2) called with the fd of a different net ns
  85  *  * unshare(2) called with CLONE_NEWNET
  86  */
  87 void lttng_context_net_ns_reset(void)
  88 {
  89         CMM_STORE_SHARED(URCU_TLS(cached_net_ns), NS_INO_UNINITIALIZED);
  90 }
  91
  92 static
  93 size_t net_ns_get_size(struct lttng_ust_ctx_field *field, size_t offset)
  94 {
  95         size_t size = 0;
  96
  97         size += lttng_ust_lib_ring_buffer_align(offset, lttng_ust_rb_alignof(ino_t));
  98         size += sizeof(ino_t);
  99         return size;
 100 }
 101
 102 static
 103 void net_ns_record(struct lttng_ust_ctx_field *field,
 104                  struct lttng_ust_lib_ring_buffer_ctx *ctx,
 105                  struct lttng_ust_channel_buffer *chan)
 106 {
 107         ino_t net_ns;
 108
 109         net_ns = get_net_ns();
 110         lttng_ust_lib_ring_buffer_align_ctx(ctx, lttng_ust_rb_alignof(net_ns));
 111         chan->ops->event_write(ctx, &net_ns, sizeof(net_ns));
 112 }
 113
 114 static
 115 void net_ns_get_value(struct lttng_ust_ctx_field *field,
 116                 struct lttng_ust_ctx_value *value)
 117 {
 118         value->u.s64 = get_net_ns();
 119 }
 120
 121 int lttng_add_net_ns_to_ctx(struct lttng_ust_ctx **ctx)
 122 {
 123         struct lttng_ust_ctx_field *field;
 124         struct lttng_ust_type_common *type;
 125         int ret;
 126
 127         type = lttng_ust_create_type_integer(sizeof(ino_t) * CHAR_BIT,
 128                         lttng_ust_rb_alignof(ino_t) * CHAR_BIT,
 129                         lttng_ust_is_signed_type(ino_t),
 130                         BYTE_ORDER, 10);
 131         if (!type)
 132                 return -ENOMEM;
 133         field = lttng_append_context(ctx);
 134         if (!field) {
 135                 ret = -ENOMEM;
 136                 goto error_context;
 137         }
 138         if (lttng_find_context(*ctx, "net_ns")) {
 139                 ret = -EEXIST;
 140                 goto error_find_context;
 141         }
 142         field->event_field->name = strdup("net_ns");
 143         if (!field->event_field->name) {
 144                 ret = -ENOMEM;
 145                 goto error_name;
 146         }
 147         field->event_field->type = type;
 148         field->get_size = net_ns_get_size;
 149         field->record = net_ns_record;
 150         field->get_value = net_ns_get_value;
 151         lttng_context_update(*ctx);
 152         return 0;
 153
 154 error_name:
 155 error_find_context:
 156         lttng_remove_context_field(ctx, field);
 157 error_context:
 158         lttng_ust_destroy_type(type);
 159         return ret;
 160 }
 161
 162 /*
 163  *  * Force a read (imply TLS fixup for dlopen) of TLS variables.
 164  *   */
 165 void lttng_fixup_net_ns_tls(void)
 166 {
 167         asm volatile ("" : : "m" (URCU_TLS(cached_net_ns)));
 168 }