Bug#357152: linked list returned by getifaddrs() contains structures without any address data

[Jan C. Nordholz]

Package: libc6
Version: 2.3.6-2

This is the list getifaddrs() returns on my system (extracted
with a short C snippet) - basic information from the contained
sockaddr's printed (and some IPs hidden for privacy). Note the
P2P interfaces:

] eth0 (flags 0x1043): Non-NULL? Addr Y Netmask - Dest/BCast Y
]  [F 17]  IFIndex 1
] lo (flags 0x49): Non-NULL? Addr Y Netmask - Dest/BCast Y
]  [F 17]  IFIndex 2
] eth1 (flags 0x1003): Non-NULL? Addr Y Netmask - Dest/BCast Y
]  [F 17]  IFIndex 3
] sit0 (flags 0x80): Non-NULL? Addr Y Netmask - Dest/BCast Y
]  [F 17]  IFIndex 4
] tap0 (flags 0x1043): Non-NULL? Addr Y Netmask - Dest/BCast Y
]  [F 17]  IFIndex 5
] tap1 (flags 0x1043): Non-NULL? Addr Y Netmask - Dest/BCast Y
]  [F 17]  IFIndex 6
] ppp0 (flags 0x10d1): Non-NULL? Addr - Netmask - Dest/BCast -
] ippp0 (flags 0xd1): Non-NULL? Addr - Netmask - Dest/BCast -
] lo (flags 0x49): Non-NULL? Addr Y Netmask Y Dest/BCast Y
]  [F 2]   Addr 0x0100007f
]          Mask 0x000000ff
] eth1 (flags 0x1003): Non-NULL? Addr Y Netmask Y Dest/BCast Y
]  [F 2]   Addr 0x3d40a8c0
]          Mask 0x00ffffff
] tap0 (flags 0x1043): Non-NULL? Addr Y Netmask Y Dest/BCast Y
]  [F 2]   Addr 0x0120a8c0
]          Mask 0x00ffffff
] tap1 (flags 0x1043): Non-NULL? Addr Y Netmask Y Dest/BCast Y
]  [F 2]   Addr 0x0121a8c0
]          Mask 0x00ffffff
] ppp0 (flags 0x10d1): Non-NULL? Addr Y Netmask Y Dest/BCast Y
]  [F 2]   Addr 0x........
]          Mask 0xffffffff
] ippp0 (flags 0xd1): Non-NULL? Addr Y Netmask Y Dest/BCast Y
]  [F 2]   Addr 0x........
]          Mask 0xffffffff
] eth0 (flags 0x1043): Non-NULL? Addr Y Netmask Y Dest/BCast -
]  [F 10]  Addr fe80000000000000................
] lo (flags 0x49): Non-NULL? Addr Y Netmask Y Dest/BCast -
]  [F 10]  Addr 00000000000000000000000000000001
] tap0 (flags 0x1043): Non-NULL? Addr Y Netmask Y Dest/BCast -
]  [F 10]  Addr fe80000000000000709548fffeed901c
] tap1 (flags 0x1043): Non-NULL? Addr Y Netmask Y Dest/BCast -
]  [F 10]  Addr fe8000000000000070f756fffec1794f

Although <ifaddrs.h> doesn't explicitly claim it, there is at least
one program that relies on ifa_addr always being non-NULL (=> #356858);
and it should be no problem to get those empty structures out of
the list.

If I find enough time, I'll try to submit a patch.


Regards,

Jan

-- 
Jan C. Nordholz
<jckn At gmx net>


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