if_nameindex.c raw

   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  }
 115