https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=b88d686a68d7bf2ff22d857a28d37fe4fdbafdf2
commit b88d686a68d7bf2ff22d857a28d37fe4fdbafdf2 Author: Ken Brown <[email protected]> Date: Mon Jul 26 10:27:53 2021 -0400 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 Diff: --- winsup/cygwin/net.cc | 29 +++++++++++++++++++++++------ 1 file changed, 23 insertions(+), 6 deletions(-) diff --git a/winsup/cygwin/net.cc b/winsup/cygwin/net.cc index 67dd7fc04..5bdc8709f 100644 --- a/winsup/cygwin/net.cc +++ b/winsup/cygwin/net.cc @@ -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); + { + inet_uton (udipa.Buffer, &addr->sin_addr); + got_addr = true; + } if (udsub.Buffer) - inet_uton (udsub.Buffer, &mask->sin_addr); + { + 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); + { + 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); + { + 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 */
