github.com/afumu/libc@v0.0.6/musl/src/network/if_nameindex.c (about)

     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  }