// DITTO VENDORING - bionic/ifaddrs.cpp, modified

/*
 * Copyright (C) 2015 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "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 THE
 * COPYRIGHT OWNER OR CONTRIBUTORS 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.
 */

#include "ifaddrs.h"

#include <errno.h>
#include <linux/if_packet.h>
#include <net/if.h>
#include <netinet/in.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

// The public ifaddrs struct is full of pointers. Rather than track several
// different allocations, we use a maximally-sized structure with the public
// part at offset 0, and pointers into its hidden tail.
struct ifaddrs_storage {
    // Must come first, so that `ifaddrs_storage` is-a `ifaddrs`.
    ifaddrs ifa;

    // The interface index, so we can match RTM_NEWADDR messages with
    // earlier RTM_NEWLINK messages (to copy the interface flags).
    int interface_index;

    // Storage for the pointers in `ifa`.
    sockaddr_storage addr;
    sockaddr_storage netmask;
    sockaddr_storage ifa_ifu;
    char name[IFNAMSIZ + 1];

    explicit ifaddrs_storage(ifaddrs** list) {
        memset(this, 0, sizeof(*this));

        // push_front onto `list`.
        ifa.ifa_next = *list;
        *list = reinterpret_cast<ifaddrs*>(this);
    }

    void SetAddress(int family, const void* data, size_t byteCount) {
        // The kernel currently uses the order IFA_ADDRESS, IFA_LOCAL, IFA_BROADCAST
        // in inet_fill_ifaddr, but let's not assume that will always be true...
        if (ifa.ifa_addr == nullptr) {
            // This is an IFA_ADDRESS and haven't seen an IFA_LOCAL yet, so assume this is the
            // local address. SetLocalAddress will fix things if we later see an IFA_LOCAL.
            ifa.ifa_addr = CopyAddress(family, data, byteCount, &addr);
        } else {
            // We already saw an IFA_LOCAL, which implies this is a destination address.
            ifa.ifa_dstaddr = CopyAddress(family, data, byteCount, &ifa_ifu);
        }
    }

    void SetBroadcastAddress(int family, const void* data, size_t byteCount) {
        // ifa_broadaddr and ifa_dstaddr overlap in a union. Unfortunately, it's possible
        // to have an interface with both. Keeping the last thing the kernel gives us seems
        // to be glibc 2.19's behavior too, so our choice is being source compatible with
        // badly-written code that assumes ifa_broadaddr and ifa_dstaddr are interchangeable
        // or supporting interfaces with both addresses configured. My assumption is that
        // bad code is more common than weird network interfaces...
        ifa.ifa_broadaddr = CopyAddress(family, data, byteCount, &ifa_ifu);
    }

    void SetLocalAddress(int family, const void* data, size_t byteCount) {
        // The kernel source says "for point-to-point IFA_ADDRESS is DESTINATION address,
        // local address is supplied in IFA_LOCAL attribute".
        //   -- http://lxr.free-electrons.com/source/include/uapi/linux/if_addr.h#L17

        // So copy any existing IFA_ADDRESS into ifa_dstaddr...
        if (ifa.ifa_addr != nullptr) {
            ifa.ifa_dstaddr = reinterpret_cast<sockaddr*>(memcpy(&ifa_ifu, &addr, sizeof(addr)));
        }
        // ...and then put this IFA_LOCAL into ifa_addr.
        ifa.ifa_addr = CopyAddress(family, data, byteCount, &addr);
    }

    // Netlink gives us the prefix length as a bit count. We need to turn
    // that into a BSD-compatible netmask represented by a sockaddr*.
    void SetNetmask(int family, size_t prefix_length) {
        // ...and work out the netmask from the prefix length.
        netmask.ss_family = family;
        uint8_t* dst = SockaddrBytes(family, &netmask);
        memset(dst, 0xff, prefix_length / 8);
        if ((prefix_length % 8) != 0) {
            dst[prefix_length/8] = (0xff << (8 - (prefix_length % 8)));
        }
        ifa.ifa_netmask = reinterpret_cast<sockaddr*>(&netmask);
    }

    void SetPacketAttributes(int ifindex, unsigned short hatype, unsigned char halen) {
        sockaddr_ll* sll = reinterpret_cast<sockaddr_ll*>(&addr);
        sll->sll_ifindex = ifindex;
        sll->sll_hatype = hatype;
        sll->sll_halen = halen;
    }

private:
    sockaddr* CopyAddress(int family, const void* data, size_t byteCount, sockaddr_storage* ss) {
        // Netlink gives us the address family in the header, and the
        // sockaddr_in or sockaddr_in6 bytes as the payload. We need to
        // stitch the two bits together into the sockaddr that's part of
        // our portable interface.
        ss->ss_family = family;
        memcpy(SockaddrBytes(family, ss), data, byteCount);

        // For IPv6 we might also have to set the scope id.
        if (family == AF_INET6 && (IN6_IS_ADDR_LINKLOCAL(data) || IN6_IS_ADDR_MC_LINKLOCAL(data))) {
            reinterpret_cast<sockaddr_in6*>(ss)->sin6_scope_id = interface_index;
        }

        return reinterpret_cast<sockaddr*>(ss);
    }

    // Returns a pointer to the first byte in the address data (which is
    // stored in network byte order).
    uint8_t* SockaddrBytes(int family, sockaddr_storage* ss) {
        if (family == AF_INET) {
            sockaddr_in* ss4 = reinterpret_cast<sockaddr_in*>(ss);
            return reinterpret_cast<uint8_t*>(&ss4->sin_addr);
        } else if (family == AF_INET6) {
            sockaddr_in6* ss6 = reinterpret_cast<sockaddr_in6*>(ss);
            return reinterpret_cast<uint8_t*>(&ss6->sin6_addr);
        } else if (family == AF_PACKET) {
            sockaddr_ll* sll = reinterpret_cast<sockaddr_ll*>(ss);
            return reinterpret_cast<uint8_t*>(&sll->sll_addr);
        }
        return nullptr;
    }
};

static void __getifaddrs_callback(void* context, nlmsghdr* hdr) {
    ifaddrs** out = reinterpret_cast<ifaddrs**>(context);

    if (hdr->nlmsg_type == RTM_NEWLINK) {
        ifinfomsg* ifi = reinterpret_cast<ifinfomsg*>(NLMSG_DATA(hdr));

        // Create a new ifaddr entry, and set the interface index and flags.
        ifaddrs_storage* new_addr = new ifaddrs_storage(out);
        new_addr->interface_index = ifi->ifi_index;
        new_addr->ifa.ifa_flags = ifi->ifi_flags;

        // Go through the various bits of information and find the name.
        rtattr* rta = IFLA_RTA(ifi);
        size_t rta_len = IFLA_PAYLOAD(hdr);
        while (RTA_OK(rta, rta_len)) {
            if (rta->rta_type == IFLA_ADDRESS) {
                if (RTA_PAYLOAD(rta) < sizeof(new_addr->addr)) {
                    new_addr->SetAddress(AF_PACKET, RTA_DATA(rta), RTA_PAYLOAD(rta));
                    new_addr->SetPacketAttributes(ifi->ifi_index, ifi->ifi_type, RTA_PAYLOAD(rta));
                }
            } else if (rta->rta_type == IFLA_BROADCAST) {
                if (RTA_PAYLOAD(rta) < sizeof(new_addr->ifa_ifu)) {
                    new_addr->SetBroadcastAddress(AF_PACKET, RTA_DATA(rta), RTA_PAYLOAD(rta));
                    new_addr->SetPacketAttributes(ifi->ifi_index, ifi->ifi_type, RTA_PAYLOAD(rta));
                }
            } else if (rta->rta_type == IFLA_IFNAME) {
                if (RTA_PAYLOAD(rta) < sizeof(new_addr->name)) {
                    memcpy(new_addr->name, RTA_DATA(rta), RTA_PAYLOAD(rta));
                    new_addr->ifa.ifa_name = new_addr->name;
                }
            }
            rta = RTA_NEXT(rta, rta_len);
        }
    } else if (hdr->nlmsg_type == RTM_NEWADDR) {
        ifaddrmsg* msg = reinterpret_cast<ifaddrmsg*>(NLMSG_DATA(hdr));

        // We might already know about this interface from an RTM_NEWLINK message.
        const ifaddrs_storage* known_addr = reinterpret_cast<const ifaddrs_storage*>(*out);
        while (known_addr != nullptr && known_addr->interface_index != static_cast<int>(msg->ifa_index)) {
            known_addr = reinterpret_cast<const ifaddrs_storage*>(known_addr->ifa.ifa_next);
        }

        // Create a new ifaddr entry, and set the interface index.
        ifaddrs_storage* new_addr = new ifaddrs_storage(out);
        new_addr->interface_index = static_cast<int>(msg->ifa_index);

        // If this is a known interface, copy what we already know.
        // If we don't know about this interface yet, we try to resolve the name and flags using ioctl
        // calls during postprocessing.
        if (known_addr != nullptr) {
            strcpy(new_addr->name, known_addr->name);
            new_addr->ifa.ifa_name = new_addr->name;
            new_addr->ifa.ifa_flags = known_addr->ifa.ifa_flags;
        }

        // Go through the various bits of information and find the name, address
        // and any broadcast/destination address.
        rtattr* rta = IFA_RTA(msg);
        size_t rta_len = IFA_PAYLOAD(hdr);
        while (RTA_OK(rta, rta_len)) {
            if (rta->rta_type == IFA_ADDRESS) {
                if (msg->ifa_family == AF_INET || msg->ifa_family == AF_INET6) {
                    new_addr->SetAddress(msg->ifa_family, RTA_DATA(rta), RTA_PAYLOAD(rta));
                    new_addr->SetNetmask(msg->ifa_family, msg->ifa_prefixlen);
                }
            } else if (rta->rta_type == IFA_BROADCAST) {
                if (msg->ifa_family == AF_INET) {
                    new_addr->SetBroadcastAddress(msg->ifa_family, RTA_DATA(rta), RTA_PAYLOAD(rta));
                    if (known_addr == nullptr) {
                        // We did not read the broadcast flag from an RTM_NEWLINK message.
                        // Ensure that it is set.
                        new_addr->ifa.ifa_flags |= IFF_BROADCAST;
                    }
                }
            } else if (rta->rta_type == IFA_LOCAL) {
                if (msg->ifa_family == AF_INET || msg->ifa_family == AF_INET6) {
                    new_addr->SetLocalAddress(msg->ifa_family, RTA_DATA(rta), RTA_PAYLOAD(rta));
                }
            } else if (rta->rta_type == IFA_LABEL) {
                if (RTA_PAYLOAD(rta) < sizeof(new_addr->name)) {
                    memcpy(new_addr->name, RTA_DATA(rta), RTA_PAYLOAD(rta));
                    new_addr->ifa.ifa_name = new_addr->name;
                }
            }
            rta = RTA_NEXT(rta, rta_len);
        }
    }
}

static void resolve_or_remove_nameless_interfaces(ifaddrs** list) {
    ifaddrs_storage* addr = reinterpret_cast<ifaddrs_storage*>(*list);
    ifaddrs_storage* prev_addr = nullptr;
    while (addr != nullptr) {
        ifaddrs* next_addr = addr->ifa.ifa_next;

        // Try resolving interfaces without a name first.
        if (strlen(addr->name) == 0) {
            if (if_indextoname(addr->interface_index, addr->name) != nullptr) {
                addr->ifa.ifa_name = addr->name;
            }
        }

        // If the interface could not be resolved, remove it.
        if (strlen(addr->name) == 0) {
            if (prev_addr == nullptr) {
                *list = next_addr;
            } else {
                prev_addr->ifa.ifa_next = next_addr;
            }
            free(addr);
        } else {
            prev_addr = addr;
        }

        addr = reinterpret_cast<ifaddrs_storage*>(next_addr);
    }
}

static void get_interface_flags_via_ioctl(ifaddrs** list) {
    ScopedFd s(socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0));
    if (s.get() == -1) {
        return;
    }

    for (ifaddrs_storage* addr = reinterpret_cast<ifaddrs_storage*>(*list); addr != nullptr;
         addr = reinterpret_cast<ifaddrs_storage*>(addr->ifa.ifa_next)) {
        ifreq ifr = {};
        strlcpy(ifr.ifr_name, addr->ifa.ifa_name, sizeof(ifr.ifr_name));
        if (ioctl(s.get(), SIOCGIFFLAGS, &ifr) != -1) {
            addr->ifa.ifa_flags = ifr.ifr_flags;
        }
    }
}

int getifaddrs(ifaddrs** out) {
    // We construct the result directly into `out`, so terminate the list.
    *out = nullptr;

    // Open the netlink socket and ask for all the links and addresses.
    NetlinkConnection nc;
    // SELinux policy only allows RTM_GETLINK messages to be sent by system apps.
    bool getlink_success = false;
    bool getaddr_success =
            nc.SendRequest(RTM_GETADDR) && nc.ReadResponses(__getifaddrs_callback, out);

    if (!getaddr_success) {
        freeifaddrs(*out);
        // Ensure that callers crash if they forget to check for success.
        *out = nullptr;
        return -1;
    }

    if (!getlink_success) {
        // If we weren't able to depend on GETLINK messages, it's possible some
        // interfaces never got their name set. Resolve them using if_indextoname or remove them.
        resolve_or_remove_nameless_interfaces(out);
        // Similarly, without GETLINK messages, interfaces will not have their flags set.
        // Resolve them using the SIOCGIFFLAGS ioctl call.
        get_interface_flags_via_ioctl(out);
    }

    return 0;
}

void freeifaddrs(ifaddrs* list) {
    while (list != nullptr) {
        ifaddrs* current = list;
        list = list->ifa_next;
        free(current);
    }
}

// DITTO VENDORING - bionic/bionic_netlink.cpp, modified

NetlinkConnection::NetlinkConnection() {
    // The kernel keeps packets under 8KiB (NLMSG_GOODSIZE),
    // but that's a bit too large to go on the stack.
    size_ = 8192;
    data_ = new char[size_];
}

NetlinkConnection::~NetlinkConnection() {
    delete[] data_;
}

bool NetlinkConnection::SendRequest(int type) {
    // Rather than force all callers to check for the unlikely event of being
    // unable to allocate 8KiB, check here.
    if (data_ == nullptr) return false;

    // Did we open a netlink socket yet?
    if (fd_.get() == -1) {
        fd_.reset(socket(PF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, NETLINK_ROUTE));
        if (fd_.get() == -1) return false;
    }

    // Construct and send the message.
    struct NetlinkMessage {
        nlmsghdr hdr;
        rtgenmsg msg;
    } request;
    memset(&request, 0, sizeof(request));
    request.hdr.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST;
    request.hdr.nlmsg_type = type;
    request.hdr.nlmsg_len = sizeof(request);
    request.msg.rtgen_family = AF_UNSPEC; // All families.
    return (TEMP_FAILURE_RETRY(send(fd_.get(), &request, sizeof(request), 0)) == sizeof(request));
}

bool NetlinkConnection::ReadResponses(void callback(void*, nlmsghdr*), void* context) {
    // Read through all the responses, handing interesting ones to the callback.
    ssize_t bytes_read;
    while ((bytes_read = TEMP_FAILURE_RETRY(recv(fd_.get(), data_, size_, 0))) > 0) {
        nlmsghdr* hdr = reinterpret_cast<nlmsghdr*>(data_);
        for (; NLMSG_OK(hdr, static_cast<size_t>(bytes_read)); hdr = NLMSG_NEXT(hdr, bytes_read)) {
            if (hdr->nlmsg_type == NLMSG_DONE) return true;
            if (hdr->nlmsg_type == NLMSG_ERROR) {
                nlmsgerr* err = reinterpret_cast<nlmsgerr*>(NLMSG_DATA(hdr));
                errno = (hdr->nlmsg_len >= NLMSG_LENGTH(sizeof(nlmsgerr))) ? -err->error : EIO;
                return false;
            }
            callback(context, hdr);
        }
    }

    // We only get here if recv fails before we see a NLMSG_DONE.
    return false;
}