Single include file based on another fix used to solve the ifaddrs.h missing problem with termux on android. This is a problem when building pyzmq/libzmq FYI:both will fail for other diferent reasons, but this is a usefull fix. I do not know anything about the code quality, i had to fix untyped mallocs, but i guess they get freed somewhere right…

ifaddrs.h

/*
 * Copyright (c) 1995, 1999
 *	Berkeley Software Design, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * THIS SOFTWARE IS PROVIDED BY Berkeley Software Design, Inc. ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL Berkeley Software Design, Inc. BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	BSDI ifaddrs.h,v 2.5 2000/02/23 14:51:59 dab Exp
 */

#ifndef	_IFADDRS_H_
#define	_IFADDRS_H_

struct ifaddrs {
	struct ifaddrs  *ifa_next;
	char		*ifa_name;
	unsigned int	 ifa_flags;
	struct sockaddr	*ifa_addr;
	struct sockaddr	*ifa_netmask;
	struct sockaddr	*ifa_dstaddr;
	void		*ifa_data;
};

/*
 * This may have been defined in <net/if.h>.  Note that if <net/if.h> is
 * to be included it must be included before this header file.
 */
#ifndef	ifa_broadaddr
#define	ifa_broadaddr	ifa_dstaddr	/* broadcast address interface */
#endif

#include <sys/cdefs.h>

__BEGIN_DECLS
extern int getifaddrs(struct ifaddrs **ifap);
extern void freeifaddrs(struct ifaddrs *ifa);
__END_DECLS

#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include <net/if_arp.h>
#include <netinet/in.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>

typedef struct NetlinkList
{
    struct NetlinkList *m_next;
    struct nlmsghdr *m_data;
    unsigned int m_size;
} NetlinkList;

static int netlink_socket(void)
{
    int l_socket = socket(PF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
    if(l_socket < 0)
    {
        return -1;
    }
    
    struct sockaddr_nl l_addr;
    memset(&l_addr, 0, sizeof(l_addr));
    l_addr.nl_family = AF_NETLINK;
    if(bind(l_socket, (struct sockaddr *)&l_addr, sizeof(l_addr)) < 0)
    {
        close(l_socket);
        return -1;
    }
    
    return l_socket;
}

static int netlink_send(int p_socket, int p_request)
{
    char l_buffer[NLMSG_ALIGN(sizeof(struct nlmsghdr)) + NLMSG_ALIGN(sizeof(struct rtgenmsg))];
    memset(l_buffer, 0, sizeof(l_buffer));
    struct nlmsghdr *l_hdr = (struct nlmsghdr *)l_buffer;
    struct rtgenmsg *l_msg = (struct rtgenmsg *)NLMSG_DATA(l_hdr);
    
    l_hdr->nlmsg_len = NLMSG_LENGTH(sizeof(*l_msg));
    l_hdr->nlmsg_type = p_request;
    l_hdr->nlmsg_flags = NLM_F_ROOT | NLM_F_MATCH | NLM_F_REQUEST;
    l_hdr->nlmsg_pid = 0;
    l_hdr->nlmsg_seq = p_socket;
    l_msg->rtgen_family = AF_UNSPEC;
    
    struct sockaddr_nl l_addr;
    memset(&l_addr, 0, sizeof(l_addr));
    l_addr.nl_family = AF_NETLINK;
    return (sendto(p_socket, l_hdr, l_hdr->nlmsg_len, 0, (struct sockaddr *)&l_addr, sizeof(l_addr)));
}

static int netlink_recv(int p_socket, void *p_buffer, size_t p_len)
{
    struct msghdr l_msg;
    struct iovec l_iov = { p_buffer, p_len };
    struct sockaddr_nl l_addr;
    int l_result;

    for(;;)
    {
        l_msg.msg_name = (void *)&l_addr;
        l_msg.msg_namelen = sizeof(l_addr);
        l_msg.msg_iov = &l_iov;
        l_msg.msg_iovlen = 1;
        l_msg.msg_control = NULL;
        l_msg.msg_controllen = 0;
        l_msg.msg_flags = 0;
        int l_result = recvmsg(p_socket, &l_msg, 0);
        
        if(l_result < 0)
        {
            if(errno == EINTR)
            {
                continue;
            }
            return -2;
        }
        
        if(l_msg.msg_flags & MSG_TRUNC)
        { // buffer was too small
            return -1;
        }
        return l_result;
    }
}

static struct nlmsghdr *getNetlinkResponse(int p_socket, int *p_size, int *p_done)
{
    size_t l_size = 4096;
    nlmsghdr *l_buffer = NULL;
    
    for(;;)
    {
        free(l_buffer);-<
        l_buffer = (nlmsghdr *) malloc(l_size);
        
        int l_read = netlink_recv(p_socket, l_buffer, l_size);
        *p_size = l_read;
        if(l_read == -2)
        {
            free(l_buffer);
            return NULL;
        }
        if(l_read >= 0)
        {
            pid_t l_pid = getpid();
            struct nlmsghdr *l_hdr;
            for(l_hdr = (struct nlmsghdr *)l_buffer; NLMSG_OK(l_hdr, (unsigned int)l_read); l_hdr = (struct nlmsghdr *)NLMSG_NEXT(l_hdr, l_read))
            {
                if((pid_t)l_hdr->nlmsg_pid != l_pid || (int)l_hdr->nlmsg_seq != p_socket)
                {
                    continue;
                }
                
                if(l_hdr->nlmsg_type == NLMSG_DONE)
                {
                    *p_done = 1;
                    break;
                }
                
                if(l_hdr->nlmsg_type == NLMSG_ERROR)
                {
                    free(l_buffer);
                    return NULL;
                }
            }
            return l_buffer;
        }
        
        l_size *= 2;
    }
}

static NetlinkList *newListItem(struct nlmsghdr *p_data, unsigned int p_size)
{
  NetlinkList *l_item = (NetlinkList *) malloc(sizeof(NetlinkList));
    l_item->m_next = NULL;
    l_item->m_data = p_data;
    l_item->m_size = p_size;
    return l_item;
}

static void freeResultList(NetlinkList *p_list)
{
    NetlinkList *l_cur;
    while(p_list)
    {
        l_cur = p_list;
        p_list = p_list->m_next;
        free(l_cur->m_data);
        free(l_cur);
    }
}

static NetlinkList *getResultList(int p_socket, int p_request)
{
    if(netlink_send(p_socket, p_request) < 0)
    {
        return NULL;
    }

    NetlinkList *l_list = NULL;
    NetlinkList *l_end = NULL;
    int l_size;
    int l_done = 0;
    while(!l_done)
    {
        struct nlmsghdr *l_hdr = getNetlinkResponse(p_socket, &l_size, &l_done);
        if(!l_hdr)
        { // error
            freeResultList(l_list);
            return NULL;
        }
        
        NetlinkList *l_item = newListItem(l_hdr, l_size);
        if(!l_list)
        {
            l_list = l_item;
        }
        else
        {
            l_end->m_next = l_item;
        }
        l_end = l_item;
    }
    return l_list;
}

static size_t maxSize(size_t a, size_t b)
{
    return (a > b ? a : b);
}

static size_t calcAddrLen(sa_family_t p_family, int p_dataSize)
{
    switch(p_family)
    {
        case AF_INET:
            return sizeof(struct sockaddr_in);
        case AF_INET6:
            return sizeof(struct sockaddr_in6);
        case AF_PACKET:
            return maxSize(sizeof(struct sockaddr_ll), offsetof(struct sockaddr_ll, sll_addr) + p_dataSize);
        default:
            return maxSize(sizeof(struct sockaddr), offsetof(struct sockaddr, sa_data) + p_dataSize);
    }
}

static void makeSockaddr(sa_family_t p_family, struct sockaddr *p_dest, void *p_data, size_t p_size)
{
    switch(p_family)
    {
        case AF_INET:
            memcpy(&((struct sockaddr_in*)p_dest)->sin_addr, p_data, p_size);
            break;
        case AF_INET6:
            memcpy(&((struct sockaddr_in6*)p_dest)->sin6_addr, p_data, p_size);
            break;
        case AF_PACKET:
            memcpy(((struct sockaddr_ll*)p_dest)->sll_addr, p_data, p_size);
            ((struct sockaddr_ll*)p_dest)->sll_halen = p_size;
            break;
        default:
            memcpy(p_dest->sa_data, p_data, p_size);
            break;
    }
    p_dest->sa_family = p_family;
}

static void addToEnd(struct ifaddrs **p_resultList, struct ifaddrs *p_entry)
{
    if(!*p_resultList)
    {
        *p_resultList = p_entry;
    }
    else
    {
        struct ifaddrs *l_cur = *p_resultList;
        while(l_cur->ifa_next)
        {
            l_cur = l_cur->ifa_next;
        }
        l_cur->ifa_next = p_entry;
    }
}

static void interpretLink(struct nlmsghdr *p_hdr, struct ifaddrs **p_links, struct ifaddrs **p_resultList)
{
    struct ifinfomsg *l_info = (struct ifinfomsg *)NLMSG_DATA(p_hdr);

    size_t l_nameSize = 0;
    size_t l_addrSize = 0;
    size_t l_dataSize = 0;
    
    size_t l_rtaSize = NLMSG_PAYLOAD(p_hdr, sizeof(struct ifinfomsg));
    struct rtattr *l_rta;
    for(l_rta = (struct rtattr *)(((char *)l_info) + NLMSG_ALIGN(sizeof(struct ifinfomsg))); RTA_OK(l_rta, l_rtaSize); l_rta = RTA_NEXT(l_rta, l_rtaSize))
    {
        void *l_rtaData = RTA_DATA(l_rta);
        size_t l_rtaDataSize = RTA_PAYLOAD(l_rta);
        switch(l_rta->rta_type)
        {
            case IFLA_ADDRESS:
            case IFLA_BROADCAST:
                l_addrSize += NLMSG_ALIGN(calcAddrLen(AF_PACKET, l_rtaDataSize));
                break;
            case IFLA_IFNAME:
                l_nameSize += NLMSG_ALIGN(l_rtaSize + 1);
                break;
            case IFLA_STATS:
                l_dataSize += NLMSG_ALIGN(l_rtaSize);
                break;
            default:
                break;
        }
    }
    
    struct ifaddrs *l_entry = (ifaddrs *) malloc(sizeof(struct ifaddrs) + l_nameSize + l_addrSize + l_dataSize);
    memset(l_entry, 0, sizeof(struct ifaddrs));
    l_entry->ifa_name = "";
    
    char *l_name = ((char *)l_entry) + sizeof(struct ifaddrs);
    char *l_addr = l_name + l_nameSize;
    char *l_data = l_addr + l_addrSize;
    
    l_entry->ifa_flags = l_info->ifi_flags;
    
    l_rtaSize = NLMSG_PAYLOAD(p_hdr, sizeof(struct ifinfomsg));
    for(l_rta = (struct rtattr *)(((char *)l_info) + NLMSG_ALIGN(sizeof(struct ifinfomsg))); RTA_OK(l_rta, l_rtaSize); l_rta = RTA_NEXT(l_rta, l_rtaSize))
    {
        void *l_rtaData = RTA_DATA(l_rta);
        size_t l_rtaDataSize = RTA_PAYLOAD(l_rta);
        switch(l_rta->rta_type)
        {
            case IFLA_ADDRESS:
            case IFLA_BROADCAST:
            {
                size_t l_addrLen = calcAddrLen(AF_PACKET, l_rtaDataSize);
                makeSockaddr(AF_PACKET, (struct sockaddr *)l_addr, l_rtaData, l_rtaDataSize);
                ((struct sockaddr_ll *)l_addr)->sll_ifindex = l_info->ifi_index;
                ((struct sockaddr_ll *)l_addr)->sll_hatype = l_info->ifi_type;
                if(l_rta->rta_type == IFLA_ADDRESS)
                {
                    l_entry->ifa_addr = (struct sockaddr *)l_addr;
                }
                else
                {
                    l_entry->ifa_broadaddr = (struct sockaddr *)l_addr;
                }
                l_addr += NLMSG_ALIGN(l_addrLen);
                break;
            }
            case IFLA_IFNAME:
              strncpy(l_name, (const char *) l_rtaData, l_rtaDataSize);
                l_name[l_rtaDataSize] = '\0';
                l_entry->ifa_name = l_name;
                break;
            case IFLA_STATS:
                memcpy(l_data, l_rtaData, l_rtaDataSize);
                l_entry->ifa_data = l_data;
                break;
            default:
                break;
        }
    }
    
    addToEnd(p_resultList, l_entry);
    p_links[l_info->ifi_index - 1] = l_entry;
}

static void interpretAddr(struct nlmsghdr *p_hdr, struct ifaddrs **p_links, struct ifaddrs **p_resultList)
{
    struct ifaddrmsg *l_info = (struct ifaddrmsg *)NLMSG_DATA(p_hdr);

    size_t l_nameSize = 0;
    size_t l_addrSize = 0;
    
    int l_addedNetmask = 0;
    
    size_t l_rtaSize = NLMSG_PAYLOAD(p_hdr, sizeof(struct ifaddrmsg));
    struct rtattr *l_rta;
    for(l_rta = (struct rtattr *)(((char *)l_info) + NLMSG_ALIGN(sizeof(struct ifaddrmsg))); RTA_OK(l_rta, l_rtaSize); l_rta = RTA_NEXT(l_rta, l_rtaSize))
    {
        void *l_rtaData = RTA_DATA(l_rta);
        size_t l_rtaDataSize = RTA_PAYLOAD(l_rta);
        if(l_info->ifa_family == AF_PACKET)
        {
            continue;
        }
        
        switch(l_rta->rta_type)
        {
            case IFA_ADDRESS:
            case IFA_LOCAL:
                if((l_info->ifa_family == AF_INET || l_info->ifa_family == AF_INET6) && !l_addedNetmask)
                { // make room for netmask
                    l_addrSize += NLMSG_ALIGN(calcAddrLen(l_info->ifa_family, l_rtaDataSize));
                    l_addedNetmask = 1;
                }
            case IFA_BROADCAST:
                l_addrSize += NLMSG_ALIGN(calcAddrLen(l_info->ifa_family, l_rtaDataSize));
                break;
            case IFA_LABEL:
                l_nameSize += NLMSG_ALIGN(l_rtaSize + 1);
                break;
            default:
                break;
        }
    }
    
    struct ifaddrs *l_entry = (ifaddrs *) malloc(sizeof(struct ifaddrs) + l_nameSize + l_addrSize);
    memset(l_entry, 0, sizeof(struct ifaddrs));
    l_entry->ifa_name = p_links[l_info->ifa_index - 1]->ifa_name;
    
    char *l_name = ((char *)l_entry) + sizeof(struct ifaddrs);
    char *l_addr = l_name + l_nameSize;
    
    l_entry->ifa_flags = l_info->ifa_flags | p_links[l_info->ifa_index - 1]->ifa_flags;
    
    l_rtaSize = NLMSG_PAYLOAD(p_hdr, sizeof(struct ifaddrmsg));
    for(l_rta = (struct rtattr *)(((char *)l_info) + NLMSG_ALIGN(sizeof(struct ifaddrmsg))); RTA_OK(l_rta, l_rtaSize); l_rta = RTA_NEXT(l_rta, l_rtaSize))
    {
        void *l_rtaData = RTA_DATA(l_rta);
        size_t l_rtaDataSize = RTA_PAYLOAD(l_rta);
        switch(l_rta->rta_type)
        {
            case IFA_ADDRESS:
            case IFA_BROADCAST:
            case IFA_LOCAL:
            {
                size_t l_addrLen = calcAddrLen(l_info->ifa_family, l_rtaDataSize);
                makeSockaddr(l_info->ifa_family, (struct sockaddr *)l_addr, l_rtaData, l_rtaDataSize);
                if(l_info->ifa_family == AF_INET6)
                {
                    if(IN6_IS_ADDR_LINKLOCAL((struct in6_addr *)l_rtaData) || IN6_IS_ADDR_MC_LINKLOCAL((struct in6_addr *)l_rtaData))
                    {
                        ((struct sockaddr_in6 *)l_addr)->sin6_scope_id = l_info->ifa_index;
                    }
                }
                
                if(l_rta->rta_type == IFA_ADDRESS)
                { // apparently in a point-to-point network IFA_ADDRESS contains the dest address and IFA_LOCAL contains the local address
                    if(l_entry->ifa_addr)
                    {
                        l_entry->ifa_dstaddr = (struct sockaddr *)l_addr;
                    }
                    else
                    {
                        l_entry->ifa_addr = (struct sockaddr *)l_addr;
                    }
                }
                else if(l_rta->rta_type == IFA_LOCAL)
                {
                    if(l_entry->ifa_addr)
                    {
                        l_entry->ifa_dstaddr = l_entry->ifa_addr;
                    }
                    l_entry->ifa_addr = (struct sockaddr *)l_addr;
                }
                else
                {
                    l_entry->ifa_broadaddr = (struct sockaddr *)l_addr;
                }
                l_addr += NLMSG_ALIGN(l_addrLen);
                break;
            }
            case IFA_LABEL:
                strncpy(l_name, (const char *) l_rtaData, l_rtaDataSize);
                l_name[l_rtaDataSize] = '\0';
                l_entry->ifa_name = l_name;
                break;
            default:
                break;
        }
    }
    
    if(l_entry->ifa_addr && (l_entry->ifa_addr->sa_family == AF_INET || l_entry->ifa_addr->sa_family == AF_INET6))
    {
        unsigned l_maxPrefix = (l_entry->ifa_addr->sa_family == AF_INET ? 32 : 128);
        unsigned l_prefix = (l_info->ifa_prefixlen > l_maxPrefix ? l_maxPrefix : l_info->ifa_prefixlen);
        char l_mask[16] = {0};
        unsigned i;
        for(i=0; i<(l_prefix/8); ++i)
        {
            l_mask[i] = 0xff;
        }
        l_mask[i] = 0xff << (8 - (l_prefix % 8));
        
        makeSockaddr(l_entry->ifa_addr->sa_family, (struct sockaddr *)l_addr, l_mask, l_maxPrefix / 8);
        l_entry->ifa_netmask = (struct sockaddr *)l_addr;
    }
    
    addToEnd(p_resultList, l_entry);
}

static void interpret(int p_socket, NetlinkList *p_netlinkList, struct ifaddrs **p_links, struct ifaddrs **p_resultList)
{
    pid_t l_pid = getpid();
    for(; p_netlinkList; p_netlinkList = p_netlinkList->m_next)
    {
        unsigned int l_nlsize = p_netlinkList->m_size;
        struct nlmsghdr *l_hdr;
        for(l_hdr = p_netlinkList->m_data; NLMSG_OK(l_hdr, l_nlsize); l_hdr = NLMSG_NEXT(l_hdr, l_nlsize))
        {
            if((pid_t)l_hdr->nlmsg_pid != l_pid || (int)l_hdr->nlmsg_seq != p_socket)
            {
                continue;
            }
            
            if(l_hdr->nlmsg_type == NLMSG_DONE)
            {
                break;
            }
            
            if(l_hdr->nlmsg_type == RTM_NEWLINK)
            {
                interpretLink(l_hdr, p_links, p_resultList);
            }
            else if(l_hdr->nlmsg_type == RTM_NEWADDR)
            {
                interpretAddr(l_hdr, p_links, p_resultList);
            }
        }
    }
}

static unsigned countLinks(int p_socket, NetlinkList *p_netlinkList)
{
    unsigned l_links = 0;
    pid_t l_pid = getpid();
    for(; p_netlinkList; p_netlinkList = p_netlinkList->m_next)
    {
        unsigned int l_nlsize = p_netlinkList->m_size;
        struct nlmsghdr *l_hdr;
        for(l_hdr = p_netlinkList->m_data; NLMSG_OK(l_hdr, l_nlsize); l_hdr = NLMSG_NEXT(l_hdr, l_nlsize))
        {
            if((pid_t)l_hdr->nlmsg_pid != l_pid || (int)l_hdr->nlmsg_seq != p_socket)
            {
                continue;
            }
            
            if(l_hdr->nlmsg_type == NLMSG_DONE)
            {
                break;
            }
            
            if(l_hdr->nlmsg_type == RTM_NEWLINK)
            {
                ++l_links;
            }
        }
    }
    
    return l_links;
}

int getifaddrs(struct ifaddrs **ifap)
{
    if(!ifap)
    {
        return -1;
    }
    *ifap = NULL;
    
    int l_socket = netlink_socket();
    if(l_socket < 0)
    {
        return -1;
    }
    
    NetlinkList *l_linkResults = getResultList(l_socket, RTM_GETLINK);
    if(!l_linkResults)
    {
        close(l_socket);
        return -1;
    }
    
    NetlinkList *l_addrResults = getResultList(l_socket, RTM_GETADDR);
    if(!l_addrResults)
    {
        close(l_socket);
        freeResultList(l_linkResults);
        return -1;
    }
    
    unsigned l_numLinks = countLinks(l_socket, l_linkResults) + countLinks(l_socket, l_addrResults);
    struct ifaddrs *l_links[l_numLinks];
    memset(l_links, 0, l_numLinks * sizeof(struct ifaddrs *));
    
    interpret(l_socket, l_linkResults, l_links, ifap);
    interpret(l_socket, l_addrResults, l_links, ifap);

    freeResultList(l_linkResults);
    freeResultList(l_addrResults);
    close(l_socket);
    return 0;
}

void freeifaddrs(struct ifaddrs *ifa)
{
    struct ifaddrs *l_cur;
    while(ifa)
    {
        l_cur = ifa;
        ifa = ifa->ifa_next;
        free(l_cur);
    }
}

#endif