src/network/if_nameindex.c

   1 #define _GNU_SOURCE
   2 #include <net/if.h>
   3 #include <errno.h>
   4 #include <unistd.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <pthread.h>
   8 #include "netlink.h"
   9
  10 #define IFADDRS_HASH_SIZE 64
  11
  12 struct ifnamemap {
  13         unsigned int hash_next;
  14         unsigned int index;
  15         unsigned char namelen;
  16         char name[IFNAMSIZ];
  17 };
  18
  19 struct ifnameindexctx {
  20         unsigned int num, allocated, str_bytes;
  21         struct ifnamemap *list;
  22         unsigned int hash[IFADDRS_HASH_SIZE];
  23 };
  24
  25 static int netlink_msg_to_nameindex(void *pctx, struct nlmsghdr *h)
  26 {
  27         struct ifnameindexctx *ctx = pctx;
  28         struct ifnamemap *map;
  29         struct rtattr *rta;
  30         unsigned int i;
  31         int index, type, namelen, bucket;
  32
  33         if (h->nlmsg_type == RTM_NEWLINK) {
  34                 struct ifinfomsg *ifi = NLMSG_DATA(h);
  35                 index = ifi->ifi_index;
  36                 type = IFLA_IFNAME;
  37                 rta = NLMSG_RTA(h, sizeof(*ifi));
  38         } else {
  39                 struct ifaddrmsg *ifa = NLMSG_DATA(h);
  40                 index = ifa->ifa_index;
  41                 type = IFA_LABEL;
  42                 rta = NLMSG_RTA(h, sizeof(*ifa));
  43         }
  44         for (; NLMSG_RTAOK(rta, h); rta = RTA_NEXT(rta)) {
  45                 if (rta->rta_type != type) continue;
  46
  47                 namelen = RTA_DATALEN(rta) - 1;
  48                 if (namelen > IFNAMSIZ) return 0;
  49
  50                 /* suppress duplicates */
  51                 bucket = index % IFADDRS_HASH_SIZE;
  52                 i = ctx->hash[bucket];
  53                 while (i) {
  54                         map = &ctx->list[i-1];
  55                         if (map->index == index &&
  56                             map->namelen == namelen &&
  57                             memcmp(map->name, RTA_DATA(rta), namelen) == 0)
  58                                 return 0;
  59                         i = map->hash_next;
  60                 }
  61
  62                 if (ctx->num >= ctx->allocated) {
  63                         size_t a = ctx->allocated ? ctx->allocated * 2 + 1 : 8;
  64                         if (a > SIZE_MAX/sizeof *map) return -1;
  65                         map = realloc(ctx->list, a * sizeof *map);
  66                         if (!map) return -1;
  67                         ctx->list = map;
  68                         ctx->allocated = a;
  69                 }
  70                 map = &ctx->list[ctx->num];
  71                 map->index = index;
  72                 map->namelen = namelen;
  73                 memcpy(map->name, RTA_DATA(rta), namelen);
  74                 ctx->str_bytes += namelen + 1;
  75                 ctx->num++;
  76                 map->hash_next = ctx->hash[bucket];
  77                 ctx->hash[bucket] = ctx->num;
  78                 return 0;
  79         }
  80         return 0;
  81 }
  82
  83 struct if_nameindex *if_nameindex()
  84 {
  85         struct ifnameindexctx _ctx, *ctx = &_ctx;
  86         struct if_nameindex *ifs = 0, *d;
  87         struct ifnamemap *s;
  88         char *p;
  89         int i;
  90         int cs;
  91
  92         pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
  93         memset(ctx, 0, sizeof(*ctx));
  94         if (__rtnetlink_enumerate(AF_UNSPEC, AF_INET, netlink_msg_to_nameindex, ctx) < 0) goto err;
  95
  96         ifs = malloc(sizeof(struct if_nameindex[ctx->num+1]) + ctx->str_bytes);
  97         if (!ifs) goto err;
  98
  99         p = (char*)(ifs + ctx->num + 1);
 100         for (i = ctx->num, d = ifs, s = ctx->list; i; i--, s++, d++) {
 101                 d->if_index = s->index;
 102                 d->if_name = p;
 103                 memcpy(p, s->name, s->namelen);
 104                 p += s->namelen;
 105                 *p++ = 0;
 106         }
 107         d->if_index = 0;
 108         d->if_name = 0;
 109 err:
 110         pthread_setcancelstate(cs, 0);
 111         free(ctx->list);
 112         errno = ENOBUFS;
 113         return ifs;
 114 }