| diff --git a/resolv/nss_dns/dns-host.c b/resolv/nss_dns/dns-host.c |
| index f8f192e..e66c6ea 100644 |
| --- a/resolv/nss_dns/dns-host.c |
| +++ b/resolv/nss_dns/dns-host.c |
| @@ -1049,7 +1049,10 @@ gaih_getanswer_slice (const querybuf *answer, int anslen, const char *qname, |
| int h_namelen = 0; |
| |
| if (ancount == 0) |
| - return NSS_STATUS_NOTFOUND; |
| + { |
| + *h_errnop = HOST_NOT_FOUND; |
| + return NSS_STATUS_NOTFOUND; |
| + } |
| |
| while (ancount-- > 0 && cp < end_of_message && had_error == 0) |
| { |
| @@ -1226,7 +1229,14 @@ gaih_getanswer_slice (const querybuf *answer, int anslen, const char *qname, |
| /* Special case here: if the resolver sent a result but it only |
| contains a CNAME while we are looking for a T_A or T_AAAA record, |
| we fail with NOTFOUND instead of TRYAGAIN. */ |
| - return canon == NULL ? NSS_STATUS_TRYAGAIN : NSS_STATUS_NOTFOUND; |
| + if (canon != NULL) |
| + { |
| + *h_errnop = HOST_NOT_FOUND; |
| + return NSS_STATUS_NOTFOUND; |
| + } |
| + |
| + *h_errnop = NETDB_INTERNAL; |
| + return NSS_STATUS_TRYAGAIN; |
| } |
| |
| |
| @@ -1240,11 +1250,101 @@ gaih_getanswer (const querybuf *answer1, int anslen1, const querybuf *answer2, |
| |
| enum nss_status status = NSS_STATUS_NOTFOUND; |
| |
| + /* Combining the NSS status of two distinct queries requires some |
| + compromise and attention to symmetry (A or AAAA queries can be |
| + returned in any order). What follows is a breakdown of how this |
| + code is expected to work and why. We discuss only SUCCESS, |
| + TRYAGAIN, NOTFOUND and UNAVAIL, since they are the only returns |
| + that apply (though RETURN and MERGE exist). We make a distinction |
| + between TRYAGAIN (recoverable) and TRYAGAIN' (not-recoverable). |
| + A recoverable TRYAGAIN is almost always due to buffer size issues |
| + and returns ERANGE in errno and the caller is expected to retry |
| + with a larger buffer. |
| + |
| + Lastly, you may be tempted to make significant changes to the |
| + conditions in this code to bring about symmetry between responses. |
| + Please don't change anything without due consideration for |
| + expected application behaviour. Some of the synthesized responses |
| + aren't very well thought out and sometimes appear to imply that |
| + IPv4 responses are always answer 1, and IPv6 responses are always |
| + answer 2, but that's not true (see the implemetnation of send_dg |
| + and send_vc to see response can arrive in any order, particlarly |
| + for UDP). However, we expect it holds roughly enough of the time |
| + that this code works, but certainly needs to be fixed to make this |
| + a more robust implementation. |
| + |
| + ---------------------------------------------- |
| + | Answer 1 Status / | Synthesized | Reason | |
| + | Answer 2 Status | Status | | |
| + |--------------------------------------------| |
| + | SUCCESS/SUCCESS | SUCCESS | [1] | |
| + | SUCCESS/TRYAGAIN | TRYAGAIN | [5] | |
| + | SUCCESS/TRYAGAIN' | SUCCESS | [1] | |
| + | SUCCESS/NOTFOUND | SUCCESS | [1] | |
| + | SUCCESS/UNAVAIL | SUCCESS | [1] | |
| + | TRYAGAIN/SUCCESS | TRYAGAIN | [2] | |
| + | TRYAGAIN/TRYAGAIN | TRYAGAIN | [2] | |
| + | TRYAGAIN/TRYAGAIN' | TRYAGAIN | [2] | |
| + | TRYAGAIN/NOTFOUND | TRYAGAIN | [2] | |
| + | TRYAGAIN/UNAVAIL | TRYAGAIN | [2] | |
| + | TRYAGAIN'/SUCCESS | SUCCESS | [3] | |
| + | TRYAGAIN'/TRYAGAIN | TRYAGAIN | [3] | |
| + | TRYAGAIN'/TRYAGAIN' | TRYAGAIN' | [3] | |
| + | TRYAGAIN'/NOTFOUND | TRYAGAIN' | [3] | |
| + | TRYAGAIN'/UNAVAIL | UNAVAIL | [3] | |
| + | NOTFOUND/SUCCESS | SUCCESS | [3] | |
| + | NOTFOUND/TRYAGAIN | TRYAGAIN | [3] | |
| + | NOTFOUND/TRYAGAIN' | TRYAGAIN' | [3] | |
| + | NOTFOUND/NOTFOUND | NOTFOUND | [3] | |
| + | NOTFOUND/UNAVAIL | UNAVAIL | [3] | |
| + | UNAVAIL/SUCCESS | UNAVAIL | [4] | |
| + | UNAVAIL/TRYAGAIN | UNAVAIL | [4] | |
| + | UNAVAIL/TRYAGAIN' | UNAVAIL | [4] | |
| + | UNAVAIL/NOTFOUND | UNAVAIL | [4] | |
| + | UNAVAIL/UNAVAIL | UNAVAIL | [4] | |
| + ---------------------------------------------- |
| + |
| + [1] If the first response is a success we return success. |
| + This ignores the state of the second answer and in fact |
| + incorrectly sets errno and h_errno to that of the second |
| + answer. However because the response is a success we ignore |
| + *errnop and *h_errnop (though that means you touched errno on |
| + success). We are being conservative here and returning the |
| + likely IPv4 response in the first answer as a success. |
| + |
| + [2] If the first response is a recoverable TRYAGAIN we return |
| + that instead of looking at the second response. The |
| + expectation here is that we have failed to get an IPv4 response |
| + and should retry both queries. |
| + |
| + [3] If the first response was not a SUCCESS and the second |
| + response is not NOTFOUND (had a SUCCESS, need to TRYAGAIN, |
| + or failed entirely e.g. TRYAGAIN' and UNAVAIL) then use the |
| + result from the second response, otherwise the first responses |
| + status is used. Again we have some odd side-effects when the |
| + second response is NOTFOUND because we overwrite *errnop and |
| + *h_errnop that means that a first answer of NOTFOUND might see |
| + its *errnop and *h_errnop values altered. Whether it matters |
| + in practice that a first response NOTFOUND has the wrong |
| + *errnop and *h_errnop is undecided. |
| + |
| + [4] If the first response is UNAVAIL we return that instead of |
| + looking at the second response. The expectation here is that |
| + it will have failed similarly e.g. configuration failure. |
| + |
| + [5] Testing this code is complicated by the fact that truncated |
| + second response buffers might be returned as SUCCESS if the |
| + first answer is a SUCCESS. To fix this we add symmetry to |
| + TRYAGAIN with the second response. If the second response |
| + is a recoverable error we now return TRYAGIN even if the first |
| + response was SUCCESS. */ |
| + |
| if (anslen1 > 0) |
| status = gaih_getanswer_slice(answer1, anslen1, qname, |
| &pat, &buffer, &buflen, |
| errnop, h_errnop, ttlp, |
| &first); |
| + |
| if ((status == NSS_STATUS_SUCCESS || status == NSS_STATUS_NOTFOUND |
| || (status == NSS_STATUS_TRYAGAIN |
| /* We want to look at the second answer in case of an |
| @@ -1260,8 +1360,15 @@ gaih_getanswer (const querybuf *answer1, int anslen1, const querybuf *answer2, |
| &pat, &buffer, &buflen, |
| errnop, h_errnop, ttlp, |
| &first); |
| + /* Use the second response status in some cases. */ |
| if (status != NSS_STATUS_SUCCESS && status2 != NSS_STATUS_NOTFOUND) |
| status = status2; |
| + /* Do not return a truncated second response (unless it was |
| + unavoidable e.g. unrecoverable TRYAGAIN). */ |
| + if (status == NSS_STATUS_SUCCESS |
| + && (status2 == NSS_STATUS_TRYAGAIN |
| + && *errnop == ERANGE && *h_errnop != NO_RECOVERY)) |
| + status = NSS_STATUS_TRYAGAIN; |
| } |
| |
| return status; |
| diff --git a/resolv/res_query.c b/resolv/res_query.c |
| index 1325f97..dd87e09 100644 |
| --- a/resolv/res_query.c |
| +++ b/resolv/res_query.c |
| @@ -391,6 +391,7 @@ __libc_res_nsearch(res_state statp, |
| { |
| free (*answerp2); |
| *answerp2 = NULL; |
| + *nanswerp2 = 0; |
| } |
| } |
| |
| @@ -431,6 +432,7 @@ __libc_res_nsearch(res_state statp, |
| { |
| free (*answerp2); |
| *answerp2 = NULL; |
| + *nanswerp2 = 0; |
| } |
| |
| /* |
| @@ -502,6 +504,7 @@ __libc_res_nsearch(res_state statp, |
| { |
| free (*answerp2); |
| *answerp2 = NULL; |
| + *nanswerp2 = 0; |
| } |
| if (saved_herrno != -1) |
| RES_SET_H_ERRNO(statp, saved_herrno); |
| diff --git a/resolv/res_send.c b/resolv/res_send.c |
| index 7f2e85f..3ba53b4 100644 |
| --- a/resolv/res_send.c |
| +++ b/resolv/res_send.c |
| @@ -1,3 +1,20 @@ |
| +/* Copyright (C) 2016 Free Software Foundation, Inc. |
| + This file is part of the GNU C Library. |
| + |
| + The GNU C Library is free software; you can redistribute it and/or |
| + modify it under the terms of the GNU Lesser General Public |
| + License as published by the Free Software Foundation; either |
| + version 2.1 of the License, or (at your option) any later version. |
| + |
| + The GNU C Library is distributed in the hope that it will be useful, |
| + but WITHOUT ANY WARRANTY; without even the implied warranty of |
| + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| + Lesser General Public License for more details. |
| + |
| + You should have received a copy of the GNU Lesser General Public |
| + License along with the GNU C Library; if not, see |
| + <http://www.gnu.org/licenses/>. */ |
| + |
| /* |
| * Copyright (c) 1985, 1989, 1993 |
| * The Regents of the University of California. All rights reserved. |
| @@ -360,6 +377,8 @@ __libc_res_nsend(res_state statp, const u_char *buf, int buflen, |
| #ifdef USE_HOOKS |
| if (__builtin_expect (statp->qhook || statp->rhook, 0)) { |
| if (anssiz < MAXPACKET && ansp) { |
| + /* Always allocate MAXPACKET, callers expect |
| + this specific size. */ |
| u_char *buf = malloc (MAXPACKET); |
| if (buf == NULL) |
| return (-1); |
| @@ -652,6 +671,76 @@ libresolv_hidden_def (res_nsend) |
| |
| /* Private */ |
| |
| +/* The send_vc function is responsible for sending a DNS query over TCP |
| + to the nameserver numbered NS from the res_state STATP i.e. |
| + EXT(statp).nssocks[ns]. The function supports sending both IPv4 and |
| + IPv6 queries at the same serially on the same socket. |
| + |
| + Please note that for TCP there is no way to disable sending both |
| + queries, unlike UDP, which honours RES_SNGLKUP and RES_SNGLKUPREOP |
| + and sends the queries serially and waits for the result after each |
| + sent query. This implemetnation should be corrected to honour these |
| + options. |
| + |
| + Please also note that for TCP we send both queries over the same |
| + socket one after another. This technically violates best practice |
| + since the server is allowed to read the first query, respond, and |
| + then close the socket (to service another client). If the server |
| + does this, then the remaining second query in the socket data buffer |
| + will cause the server to send the client an RST which will arrive |
| + asynchronously and the client's OS will likely tear down the socket |
| + receive buffer resulting in a potentially short read and lost |
| + response data. This will force the client to retry the query again, |
| + and this process may repeat until all servers and connection resets |
| + are exhausted and then the query will fail. It's not known if this |
| + happens with any frequency in real DNS server implementations. This |
| + implementation should be corrected to use two sockets by default for |
| + parallel queries. |
| + |
| + The query stored in BUF of BUFLEN length is sent first followed by |
| + the query stored in BUF2 of BUFLEN2 length. Queries are sent |
| + serially on the same socket. |
| + |
| + Answers to the query are stored firstly in *ANSP up to a max of |
| + *ANSSIZP bytes. If more than *ANSSIZP bytes are needed and ANSCP |
| + is non-NULL (to indicate that modifying the answer buffer is allowed) |
| + then malloc is used to allocate a new response buffer and ANSCP and |
| + ANSP will both point to the new buffer. If more than *ANSSIZP bytes |
| + are needed but ANSCP is NULL, then as much of the response as |
| + possible is read into the buffer, but the results will be truncated. |
| + When truncation happens because of a small answer buffer the DNS |
| + packets header feild TC will bet set to 1, indicating a truncated |
| + message and the rest of the socket data will be read and discarded. |
| + |
| + Answers to the query are stored secondly in *ANSP2 up to a max of |
| + *ANSSIZP2 bytes, with the actual response length stored in |
| + *RESPLEN2. If more than *ANSSIZP bytes are needed and ANSP2 |
| + is non-NULL (required for a second query) then malloc is used to |
| + allocate a new response buffer, *ANSSIZP2 is set to the new buffer |
| + size and *ANSP2_MALLOCED is set to 1. |
| + |
| + The ANSP2_MALLOCED argument will eventually be removed as the |
| + change in buffer pointer can be used to detect the buffer has |
| + changed and that the caller should use free on the new buffer. |
| + |
| + Note that the answers may arrive in any order from the server and |
| + therefore the first and second answer buffers may not correspond to |
| + the first and second queries. |
| + |
| + It is not supported to call this function with a non-NULL ANSP2 |
| + but a NULL ANSCP. Put another way, you can call send_vc with a |
| + single unmodifiable buffer or two modifiable buffers, but no other |
| + combination is supported. |
| + |
| + It is the caller's responsibility to free the malloc allocated |
| + buffers by detecting that the pointers have changed from their |
| + original values i.e. *ANSCP or *ANSP2 has changed. |
| + |
| + If errors are encountered then *TERRNO is set to an appropriate |
| + errno value and a zero result is returned for a recoverable error, |
| + and a less-than zero result is returned for a non-recoverable error. |
| + If no errors are encountered then *TERRNO is left unmodified and |
| + a the length of the first response in bytes is returned. */ |
| static int |
| send_vc(res_state statp, |
| const u_char *buf, int buflen, const u_char *buf2, int buflen2, |
| @@ -661,11 +750,7 @@ send_vc(res_state statp, |
| { |
| const HEADER *hp = (HEADER *) buf; |
| const HEADER *hp2 = (HEADER *) buf2; |
| - u_char *ans = *ansp; |
| - int orig_anssizp = *anssizp; |
| - // XXX REMOVE |
| - // int anssiz = *anssizp; |
| - HEADER *anhp = (HEADER *) ans; |
| + HEADER *anhp = (HEADER *) *ansp; |
| struct sockaddr_in6 *nsap = EXT(statp).nsaddrs[ns]; |
| int truncating, connreset, resplen, n; |
| struct iovec iov[4]; |
| @@ -741,6 +826,8 @@ send_vc(res_state statp, |
| * Receive length & response |
| */ |
| int recvresp1 = 0; |
| + /* Skip the second response if there is no second query. |
| + To do that we mark the second response as received. */ |
| int recvresp2 = buf2 == NULL; |
| uint16_t rlen16; |
| read_len: |
| @@ -777,33 +864,14 @@ send_vc(res_state statp, |
| u_char **thisansp; |
| int *thisresplenp; |
| if ((recvresp1 | recvresp2) == 0 || buf2 == NULL) { |
| + /* We have not received any responses |
| + yet or we only have one response to |
| + receive. */ |
| thisanssizp = anssizp; |
| thisansp = anscp ?: ansp; |
| assert (anscp != NULL || ansp2 == NULL); |
| thisresplenp = &resplen; |
| } else { |
| - if (*anssizp != MAXPACKET) { |
| - /* No buffer allocated for the first |
| - reply. We can try to use the rest |
| - of the user-provided buffer. */ |
| -#ifdef _STRING_ARCH_unaligned |
| - *anssizp2 = orig_anssizp - resplen; |
| - *ansp2 = *ansp + resplen; |
| -#else |
| - int aligned_resplen |
| - = ((resplen + __alignof__ (HEADER) - 1) |
| - & ~(__alignof__ (HEADER) - 1)); |
| - *anssizp2 = orig_anssizp - aligned_resplen; |
| - *ansp2 = *ansp + aligned_resplen; |
| -#endif |
| - } else { |
| - /* The first reply did not fit into the |
| - user-provided buffer. Maybe the second |
| - answer will. */ |
| - *anssizp2 = orig_anssizp; |
| - *ansp2 = *ansp; |
| - } |
| - |
| thisanssizp = anssizp2; |
| thisansp = ansp2; |
| thisresplenp = resplen2; |
| @@ -811,10 +879,14 @@ send_vc(res_state statp, |
| anhp = (HEADER *) *thisansp; |
| |
| *thisresplenp = rlen; |
| - if (rlen > *thisanssizp) { |
| - /* Yes, we test ANSCP here. If we have two buffers |
| - both will be allocatable. */ |
| - if (__builtin_expect (anscp != NULL, 1)) { |
| + /* Is the answer buffer too small? */ |
| + if (*thisanssizp < rlen) { |
| + /* If the current buffer is not the the static |
| + user-supplied buffer then we can reallocate |
| + it. */ |
| + if (thisansp != NULL && thisansp != ansp) { |
| + /* Always allocate MAXPACKET, callers expect |
| + this specific size. */ |
| u_char *newp = malloc (MAXPACKET); |
| if (newp == NULL) { |
| *terrno = ENOMEM; |
| @@ -824,6 +896,9 @@ send_vc(res_state statp, |
| *thisanssizp = MAXPACKET; |
| *thisansp = newp; |
| anhp = (HEADER *) newp; |
| + /* A uint16_t can't be larger than MAXPACKET |
| + thus it's safe to allocate MAXPACKET but |
| + read RLEN bytes instead. */ |
| len = rlen; |
| } else { |
| Dprint(statp->options & RES_DEBUG, |
| @@ -987,6 +1062,66 @@ reopen (res_state statp, int *terrno, int ns) |
| return 1; |
| } |
| |
| +/* The send_dg function is responsible for sending a DNS query over UDP |
| + to the nameserver numbered NS from the res_state STATP i.e. |
| + EXT(statp).nssocks[ns]. The function supports IPv4 and IPv6 queries |
| + along with the ability to send the query in parallel for both stacks |
| + (default) or serially (RES_SINGLKUP). It also supports serial lookup |
| + with a close and reopen of the socket used to talk to the server |
| + (RES_SNGLKUPREOP) to work around broken name servers. |
| + |
| + The query stored in BUF of BUFLEN length is sent first followed by |
| + the query stored in BUF2 of BUFLEN2 length. Queries are sent |
| + in parallel (default) or serially (RES_SINGLKUP or RES_SNGLKUPREOP). |
| + |
| + Answers to the query are stored firstly in *ANSP up to a max of |
| + *ANSSIZP bytes. If more than *ANSSIZP bytes are needed and ANSCP |
| + is non-NULL (to indicate that modifying the answer buffer is allowed) |
| + then malloc is used to allocate a new response buffer and ANSCP and |
| + ANSP will both point to the new buffer. If more than *ANSSIZP bytes |
| + are needed but ANSCP is NULL, then as much of the response as |
| + possible is read into the buffer, but the results will be truncated. |
| + When truncation happens because of a small answer buffer the DNS |
| + packets header feild TC will bet set to 1, indicating a truncated |
| + message, while the rest of the UDP packet is discarded. |
| + |
| + Answers to the query are stored secondly in *ANSP2 up to a max of |
| + *ANSSIZP2 bytes, with the actual response length stored in |
| + *RESPLEN2. If more than *ANSSIZP bytes are needed and ANSP2 |
| + is non-NULL (required for a second query) then malloc is used to |
| + allocate a new response buffer, *ANSSIZP2 is set to the new buffer |
| + size and *ANSP2_MALLOCED is set to 1. |
| + |
| + The ANSP2_MALLOCED argument will eventually be removed as the |
| + change in buffer pointer can be used to detect the buffer has |
| + changed and that the caller should use free on the new buffer. |
| + |
| + Note that the answers may arrive in any order from the server and |
| + therefore the first and second answer buffers may not correspond to |
| + the first and second queries. |
| + |
| + It is not supported to call this function with a non-NULL ANSP2 |
| + but a NULL ANSCP. Put another way, you can call send_vc with a |
| + single unmodifiable buffer or two modifiable buffers, but no other |
| + combination is supported. |
| + |
| + It is the caller's responsibility to free the malloc allocated |
| + buffers by detecting that the pointers have changed from their |
| + original values i.e. *ANSCP or *ANSP2 has changed. |
| + |
| + If an answer is truncated because of UDP datagram DNS limits then |
| + *V_CIRCUIT is set to 1 and the return value non-zero to indicate to |
| + the caller to retry with TCP. The value *GOTSOMEWHERE is set to 1 |
| + if any progress was made reading a response from the nameserver and |
| + is used by the caller to distinguish between ECONNREFUSED and |
| + ETIMEDOUT (the latter if *GOTSOMEWHERE is 1). |
| + |
| + If errors are encountered then *TERRNO is set to an appropriate |
| + errno value and a zero result is returned for a recoverable error, |
| + and a less-than zero result is returned for a non-recoverable error. |
| + |
| + If no errors are encountered then *TERRNO is left unmodified and |
| + a the length of the first response in bytes is returned. */ |
| static int |
| send_dg(res_state statp, |
| const u_char *buf, int buflen, const u_char *buf2, int buflen2, |
| @@ -996,8 +1131,6 @@ send_dg(res_state statp, |
| { |
| const HEADER *hp = (HEADER *) buf; |
| const HEADER *hp2 = (HEADER *) buf2; |
| - u_char *ans = *ansp; |
| - int orig_anssizp = *anssizp; |
| struct timespec now, timeout, finish; |
| struct pollfd pfd[1]; |
| int ptimeout; |
| @@ -1030,6 +1163,8 @@ send_dg(res_state statp, |
| int need_recompute = 0; |
| int nwritten = 0; |
| int recvresp1 = 0; |
| + /* Skip the second response if there is no second query. |
| + To do that we mark the second response as received. */ |
| int recvresp2 = buf2 == NULL; |
| pfd[0].fd = EXT(statp).nssocks[ns]; |
| pfd[0].events = POLLOUT; |
| @@ -1193,53 +1328,53 @@ send_dg(res_state statp, |
| int *thisresplenp; |
| |
| if ((recvresp1 | recvresp2) == 0 || buf2 == NULL) { |
| + /* We have not received any responses |
| + yet or we only have one response to |
| + receive. */ |
| thisanssizp = anssizp; |
| thisansp = anscp ?: ansp; |
| assert (anscp != NULL || ansp2 == NULL); |
| thisresplenp = &resplen; |
| } else { |
| - if (*anssizp != MAXPACKET) { |
| - /* No buffer allocated for the first |
| - reply. We can try to use the rest |
| - of the user-provided buffer. */ |
| -#ifdef _STRING_ARCH_unaligned |
| - *anssizp2 = orig_anssizp - resplen; |
| - *ansp2 = *ansp + resplen; |
| -#else |
| - int aligned_resplen |
| - = ((resplen + __alignof__ (HEADER) - 1) |
| - & ~(__alignof__ (HEADER) - 1)); |
| - *anssizp2 = orig_anssizp - aligned_resplen; |
| - *ansp2 = *ansp + aligned_resplen; |
| -#endif |
| - } else { |
| - /* The first reply did not fit into the |
| - user-provided buffer. Maybe the second |
| - answer will. */ |
| - *anssizp2 = orig_anssizp; |
| - *ansp2 = *ansp; |
| - } |
| - |
| thisanssizp = anssizp2; |
| thisansp = ansp2; |
| thisresplenp = resplen2; |
| } |
| |
| if (*thisanssizp < MAXPACKET |
| - /* Yes, we test ANSCP here. If we have two buffers |
| - both will be allocatable. */ |
| - && anscp |
| + /* If the current buffer is not the the static |
| + user-supplied buffer then we can reallocate |
| + it. */ |
| + && (thisansp != NULL && thisansp != ansp) |
| #ifdef FIONREAD |
| + /* Is the size too small? */ |
| && (ioctl (pfd[0].fd, FIONREAD, thisresplenp) < 0 |
| || *thisanssizp < *thisresplenp) |
| #endif |
| - ) { |
| + ) { |
| + /* Always allocate MAXPACKET, callers expect |
| + this specific size. */ |
| u_char *newp = malloc (MAXPACKET); |
| if (newp != NULL) { |
| - *anssizp = MAXPACKET; |
| - *thisansp = ans = newp; |
| + *thisanssizp = MAXPACKET; |
| + *thisansp = newp; |
| } |
| } |
| + /* We could end up with truncation if anscp was NULL |
| + (not allowed to change caller's buffer) and the |
| + response buffer size is too small. This isn't a |
| + reliable way to detect truncation because the ioctl |
| + may be an inaccurate report of the UDP message size. |
| + Therefore we use this only to issue debug output. |
| + To do truncation accurately with UDP we need |
| + MSG_TRUNC which is only available on Linux. We |
| + can abstract out the Linux-specific feature in the |
| + future to detect truncation. */ |
| + if (__glibc_unlikely (*thisanssizp < *thisresplenp)) { |
| + Dprint(statp->options & RES_DEBUG, |
| + (stdout, ";; response may be truncated (UDP)\n") |
| + ); |
| + } |
| HEADER *anhp = (HEADER *) *thisansp; |
| socklen_t fromlen = sizeof(struct sockaddr_in6); |
| assert (sizeof(from) <= fromlen); |
