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e2e9517607
for extremely small buffer sizes, the DNS query core in __res_msend may malfunction completely, being unable to get even the headers to determine the response code. but there is also a problem for reasonable sizes under 512 bytes: __res_msend is unable to determine if the udp answer was truncated at the recv layer, in which case it may be incomplete, and res_send is then unable to honor its contract to return the length of the full, non-truncated answer. at present, res_send does not honor that contract anyway when the full answer would exceed 512 bytes, since there is no tcp fallback, but this change at least makes it consistent in a context where this is the only "full answer" to be had.
17 lines
446 B
C
17 lines
446 B
C
#include <resolv.h>
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#include <string.h>
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int __res_send(const unsigned char *msg, int msglen, unsigned char *answer, int anslen)
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{
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int r;
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if (anslen < 512) {
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unsigned char buf[512];
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r = __res_send(msg, msglen, buf, sizeof buf);
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if (r >= 0) memcpy(answer, buf, r < anslen ? r : anslen);
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return r;
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}
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r = __res_msend(1, &msg, &msglen, &answer, &anslen, anslen);
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return r<0 || !anslen ? -1 : anslen;
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}
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weak_alias(__res_send, res_send);
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