src/OS/os.c-Linux

   1 /*************************************************
   2 *     Exim - an Internet mail transport agent    *
   3 *************************************************/
   4
   5 /* Copyright (c) University of Cambridge 1997 - 2016 */
   6 /* See the file NOTICE for conditions of use and distribution. */
   7
   8 /* Linux-specific code. This is concatenated onto the generic
   9 src/os.c file. */
  10
  11
  12 /*************************************************
  13 *              Load average computation          *
  14 *************************************************/
  15
  16 /*Linux has an apparently unique way of getting the load average, so we provide
  17 a unique function here, and define OS_LOAD_AVERAGE to stop src/os.c trying to
  18 provide the function. However, when compiling os.c for utilities, we may not
  19 want this at all, so check that it isn't set first. */
  20
  21 #if !defined(OS_LOAD_AVERAGE) && defined(__linux__)
  22 #define OS_LOAD_AVERAGE
  23
  24 /* Linux has 2 ways of returning load average:
  25
  26   (1) Do a read on /proc/loadavg
  27   (2) Use the sysinfo library function and syscall
  28
  29 The latter is simpler but in Linux 2.0 - 2.2 (and probably later releases) is
  30 exceptionally slow - 10-50ms per call is not unusual and about 100x slow the
  31 first method. This cripples high performance mail servers by increasing CPU
  32 utilisation by 3-5x.
  33
  34 In Exim's very early days, it used the 1st method. Later, it switched to the
  35 2nd method. Now it tries the 1st method and falls back to the 2nd if /proc is
  36 unavailable. */
  37
  38 #include <sys/sysinfo.h>
  39
  40 static int
  41 linux_slow_getloadavg(void)
  42 {
  43 struct sysinfo s;
  44 double avg;
  45 if (sysinfo(&s) < 0) return -1;
  46 avg = (double) (s.loads[0]) / (1<<SI_LOAD_SHIFT);
  47 return (int)(avg * 1000.0);
  48 }
  49
  50 int
  51 os_getloadavg(void)
  52 {
  53 char buffer[40];
  54 double avg;
  55 int count;
  56 int fd = open ("/proc/loadavg", O_RDONLY);
  57 if (fd == -1) return linux_slow_getloadavg();
  58 count = read (fd, buffer, sizeof(buffer));
  59 (void)close (fd);
  60 if (count <= 0) return linux_slow_getloadavg();
  61 count = sscanf (buffer, "%lf", &avg);
  62 if (count < 1) return linux_slow_getloadavg();
  63 return (int)(avg * 1000.0);
  64 }
  65 #endif  /* OS_LOAD_AVERAGE */
  66
  67
  68
  69
  70
  71 /*************************************************
  72 *         Finding interface addresses            *
  73 *************************************************/
  74
  75 /* This function is not required for utilities; we cut it out if
  76 FIND_RUNNING_INTERFACES is already defined. */
  77
  78 #ifndef FIND_RUNNING_INTERFACES
  79
  80 /* This code, contributed by Jason Gunthorpe, appears to be the current
  81 way of finding IPv6 interfaces in Linux. It first calls the common function in
  82 order to find IPv4 interfaces, then grobbles around to find the others. Jason
  83 said, "This is so horrible, don't look. Slightly ripped from net-tools
  84 ifconfig." It gets called by virtue of os_find_running_interfaces being defined
  85 as a macro for os_find_running_interfaces_linux in the os.h-Linux file. */
  86
  87 ip_address_item *
  88 os_find_running_interfaces_linux(void)
  89 {
  90 ip_address_item *yield = NULL;
  91
  92 #if HAVE_IPV6
  93 ip_address_item *last = NULL;
  94 ip_address_item  *next;
  95 char addr6p[8][5];
  96 unsigned int plen, scope, dad_status, if_idx;
  97 char devname[20+1];
  98 FILE *f;
  99 #endif
 100
 101 yield = os_common_find_running_interfaces();
 102
 103 #if HAVE_IPV6
 104
 105 /* Open the /proc file; give up if we can't. */
 106
 107 if ((f = fopen("/proc/net/if_inet6", "r")) == NULL) return yield;
 108
 109 /* Pick out the data from within the file, and add it on to the chain */
 110
 111 last = yield;
 112 if (last != NULL) while (last->next != NULL) last = last->next;
 113
 114 while (fscanf(f, "%4s%4s%4s%4s%4s%4s%4s%4s %02x %02x %02x %02x %20s\n",
 115              addr6p[0], addr6p[1], addr6p[2], addr6p[3],
 116              addr6p[4], addr6p[5], addr6p[6], addr6p[7],
 117              &if_idx, &plen, &scope, &dad_status, devname) != EOF)
 118   {
 119   struct sockaddr_in6 addr;
 120
 121   /* This data has to survive for ever, so use malloc. */
 122
 123   next = store_malloc(sizeof(ip_address_item));
 124   next->next = NULL;
 125   next->port = 0;
 126   sprintf(CS next->address, "%s:%s:%s:%s:%s:%s:%s:%s",
 127          addr6p[0], addr6p[1], addr6p[2], addr6p[3],
 128          addr6p[4], addr6p[5], addr6p[6], addr6p[7]);
 129
 130   /* Normalize the representation */
 131
 132   inet_pton(AF_INET6, CS next->address, &addr.sin6_addr);
 133   inet_ntop(AF_INET6, &addr.sin6_addr, CS next->address, sizeof(next->address));
 134
 135   if (yield == NULL) yield = last = next; else
 136     {
 137     last->next = next;
 138     last = next;
 139     }
 140
 141   DEBUG(D_interface)
 142     debug_printf("Actual local interface address is %s (%s)\n", last->address,
 143       devname);
 144   }
 145 fclose(f);
 146 #endif  /* HAVE_IPV6 */
 147
 148 return yield;
 149 }
 150
 151 #endif  /* FIND_RUNNING_INTERFACES */
 152
 153
 154 /*************
 155 * Sendfile   *
 156 *************/
 157 #include <sys/sendfile.h>
 158
 159 ssize_t
 160 os_sendfile(int out, int in, off_t * off, size_t cnt)
 161 {
 162 return sendfile(out, in, off, cnt);
 163 }
 164
 165 /* End of os.c-Linux */