ganglia mtu metric BUG? on CentOS 6.x x64-白红宇

今天在添加mtu的metric时, 发现一个ganglia bug, MTU值获取的应该是所有UP端口的最小MTU值, 但是实际上得到的结果并非如此.

gmond.conf配置如下 :

gmond.confcollection_group {  collect_once = yes  time_threshold = 1200  metric {    name = "mtu"    title = "MTU"  }

所有端口的MTU,

# ifconfig -a|grep MTU          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1          BROADCAST MULTICAST  MTU:1500  Metric:1          UP LOOPBACK RUNNING  MTU:16436  Metric:1          BROADCAST MULTICAST  MTU:1500  Metric:1

UP端口的mtu最小值是第一条1500, 但是实际ganglia画出来的是回环口的MTU 16436.

ganglia mtu metric BUG? on CentOS 6.x x64 - 德哥@Digoal - PostgreSQL research

获取mtu的代码如下 :

libmetrics/linux/metrics.c

/* --------------------------------------------------------------------------- */g_val_tmtu_func ( void ){   /* We want to find the minimum MTU (Max packet size) over all UP interfaces. */   g_val_t val;   val.uint32 = get_min_mtu();   /* A val of 0 means there are no UP interfaces. Shouldn't happen. */   return val;}

libmetrics/

interface.c

intget_min_mtu( void ){  struct ifi_info *info, *n;  unsigned min_mtu_set = 0;  unsigned min_mtu = 0;  info = Get_ifi_info(AF_INET, 0);  for(n = info; n; n = n->ifi_next)    {      if(!min_mtu_set)        {          min_mtu = n->ifi_mtu;          min_mtu_set = 1;        }      else if( n->ifi_mtu < min_mtu )        {          min_mtu = n->ifi_mtu;        }    }  free_ifi_info(info);  return min_mtu;}

libmetrics/get_ifi_info.c

struct ifi_info *get_ifi_info(int family, int doaliases){        struct ifi_info         *ifi, *ifihead, **ifipnext;        int                                     sockfd, len, lastlen, flags, myflags;        char                            *ptr, *buf, lastname[IFNAMSIZ], *cptr;        struct ifconf           ifc;        struct ifreq            *ifr, ifrcopy;        struct sockaddr_in      *sinptr;        struct ifreq            mtu;#ifdef SOLARIS        int _c_virt = 0;#endif /* SOLARIS */        int _all_virt = 0;        sockfd = Socket(AF_INET, SOCK_DGRAM, 0);        if (sockfd == -1) {                err_ret("get_ifi_info error: socket returns -1");                return NULL;        }        lastlen = 0;        len = 100 * sizeof(struct ifreq);       /* initial buffer size guess */        for ( ; ; ) {                buf = Malloc(len);                ifc.ifc_len = len;                ifc.ifc_buf = buf;                if (ioctl(sockfd, SIOCGIFCONF, &ifc) < 0) {                        if (errno != EINVAL || lastlen != 0)                                err_sys("ioctl error");                } else {                        if (ifc.ifc_len == lastlen)                                break;          /* success, len has not changed */                        lastlen = ifc.ifc_len;                }                len += 10 * sizeof(struct ifreq);       /* increment */                free(buf);        }        ifihead = NULL;        ifipnext = &ifihead;        lastname[0] = 0;/* end get_ifi_info1 */.......略struct ifi_info *Get_ifi_info(int family, int doaliases){        struct ifi_info *ifi;        if ( (ifi = get_ifi_info(family, doaliases)) == NULL)                err_quit("get_ifi_info error");        return(ifi);}

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