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Use a large initial buffer in the call to GetAdaptersAddresses.

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GetAdaptersAddresses is supposed to return ERROR_BUFFER_OVERFLOW and set
len to the required size when len is too small. So normally we would
call the function once with a small len, and then again with the longer
len. But, on Windows 2003, apparently you only get ERROR_BUFFER_OVERFLOW
the *first* time you call the function with a too-small len--the next
time you get ERROR_INVALID_PARAMETER. So this function would fail the
second and later times it is called.

So, make the first call using a large len. On Windows 2003, this will
work the first time as long as there are not too many adapters. (It will
still fail with ERROR_INVALID_PARAMETER if there are too many adapters,
but this will happen infrequently because of the large buffer.) Other
systems that always return ERROR_BUFFER_OVERFLOW when appropriate will
enlarge the buffer if the initial len is too short.
This commit is contained in:
david
2012-05-10 21:29:54 +00:00
parent cc0f2e1e54
commit 25fdaf95f3
1 changed files with 15 additions and 1 deletions
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16
libdnet-stripped/src/intf-win32.c
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@@ -207,7 +207,21 @@ _refresh_tables(intf_t *intf)
ULONG len;
p = NULL;
len = 2;
/* GetAdaptersAddresses is supposed to return ERROR_BUFFER_OVERFLOW and
* set len to the required size when len is too small. So normally we
* would call the function once with a small len, and then again with
* the longer len. But, on Windows 2003, apparently you only get
* ERROR_BUFFER_OVERFLOW the *first* time you call the function with a
* too-small len--the next time you get ERROR_INVALID_PARAMETER. So this
* function would fail the second and later times it is called.
*
* So, make the first call using a large len. On Windows 2003, this will
* work the first time as long as there are not too many adapters. (It
* will still fail with ERROR_INVALID_PARAMETER if there are too many
* adapters, but this will happen infrequently because of the large
* buffer.) Other systems that always return ERROR_BUFFER_OVERFLOW when
* appropriate will enlarge the buffer if the initial len is too short. */
len = 16384;
do {
free(p);
p = malloc(len);