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