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Fix getifaddrs' handling of point-to-point interfaces.

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Also remove an if that implied that IFA_BROADCAST is a possibility for
AF_INET6.

The existing tests fail if you have a point-to-point interface configured,
so no new test necessary.

Bug: http://b/27442503
Change-Id: I4c5823b32204ae6c15527853414c2a0cef320b53
This commit is contained in:
Elliott Hughes 2016-03-01 17:27:12 -08:00
parent c199690b5f
commit ef925e50d3
1 changed files with 53 additions and 21 deletions
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74
libc/bionic/ifaddrs.cpp
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@ -68,24 +68,52 @@ struct ifaddrs_storage {
}
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.ifa_dstaddr = CopyAddress(family, data, byteCount, &ifa_ifu);
// 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);
// ...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) {
@ -97,19 +125,19 @@ struct ifaddrs_storage {
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);
// 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;
}
// 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);
return reinterpret_cast<sockaddr*>(ss);
}
// Returns a pointer to the first byte in the address data (which is
@ -192,9 +220,13 @@ static void __getifaddrs_callback(void* context, nlmsghdr* hdr) {
new_addr->SetNetmask(msg->ifa_family, msg->ifa_prefixlen);
}
} else if (rta->rta_type == IFA_BROADCAST) {
if (msg->ifa_family == AF_INET || msg->ifa_family == AF_INET6) {
if (msg->ifa_family == AF_INET) {
new_addr->SetBroadcastAddress(msg->ifa_family, RTA_DATA(rta), RTA_PAYLOAD(rta));
}
} 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));
}
}
rta = RTA_NEXT(rta, rta_len);
}