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Cygwin: getifaddrs: don't return a zero IPv4 address 

If an interface is disconnected, net.cc:get_ifs tries to fetch IPv4
addresses from the registry.  If it fails, it currently returns
pointers to sockaddr structs with zero address.  Return a NULL pointer
instead, to signal the caller of getifaddrs that we do not have a
valid struct sockaddr.

Partially addresses: https://cygwin.com/pipermail/cygwin/2021-July/248970.html
This commit is contained in:
Ken Brown 2021-07-26 10:27:53 -04:00
parent c08ee10d6b
commit b88d686a68
1 changed files with 23 additions and 6 deletions
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21
winsup/cygwin/net.cc
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@ -1595,6 +1595,7 @@ static void
get_ipv4fromreg (struct ifall *ifp, const char *name, DWORD idx)
{
WCHAR regkey[256], *c;
bool got_addr = false, got_mask = false;
c = wcpcpy (regkey, L"Tcpip\\Parameters\\Interfaces\\");
sys_mbstowcs (c, 220, name);
@ -1637,9 +1638,15 @@ get_ipv4fromreg (struct ifall *ifp, const char *name, DWORD idx)
if (dhcp)
{
if (udipa.Buffer)
{
inet_uton (udipa.Buffer, &addr->sin_addr);
got_addr = true;
}
if (udsub.Buffer)
{
inet_uton (udsub.Buffer, &mask->sin_addr);
got_mask = true;
}
}
else
{
@ -1649,7 +1656,10 @@ get_ipv4fromreg (struct ifall *ifp, const char *name, DWORD idx)
c += wcslen (c) + 1)
ifs++;
if (*c)
{
inet_uton (c, &addr->sin_addr);
got_addr = true;
}
}
if (usub.Buffer)
{
@ -1657,9 +1667,16 @@ get_ipv4fromreg (struct ifall *ifp, const char *name, DWORD idx)
c += wcslen (c) + 1)
ifs++;
if (*c)
{
inet_uton (c, &mask->sin_addr);
got_mask = true;
}
}
}
if (got_addr)
ifp->ifa_ifa.ifa_addr = (struct sockaddr *) addr;
if (got_mask)
ifp->ifa_ifa.ifa_netmask = (struct sockaddr *) mask;
if (ifp->ifa_ifa.ifa_flags & IFF_BROADCAST)
brdc->sin_addr.s_addr = (addr->sin_addr.s_addr
& mask->sin_addr.s_addr)
@ -1800,13 +1817,13 @@ get_ifs (ULONG family)
ifp->ifa_ifa.ifa_flags |= IFF_BROADCAST;
/* Address */
ifp->ifa_addr.ss_family = AF_INET;
ifp->ifa_ifa.ifa_addr = (struct sockaddr *) &ifp->ifa_addr;
ifp->ifa_ifa.ifa_addr = NULL;
/* Broadcast/Destination address */
ifp->ifa_brddstaddr.ss_family = AF_INET;
ifp->ifa_ifa.ifa_dstaddr = NULL;
/* Netmask */
ifp->ifa_netmask.ss_family = AF_INET;
ifp->ifa_ifa.ifa_netmask = (struct sockaddr *) &ifp->ifa_netmask;
ifp->ifa_ifa.ifa_netmask = NULL;
/* Try to fetch real IPv4 address information from registry. */
get_ipv4fromreg (ifp, pap->AdapterName, idx);
/* Hardware address */