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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. |
2 // Use of this source code is governed by a BSD-style license that can be | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 // The rules for header parsing were borrowed from Firefox: | 5 // The rules for header parsing were borrowed from Firefox: |
6 // http://lxr.mozilla.org/seamonkey/source/netwerk/protocol/http/src/nsHttpRespo
nseHead.cpp | 6 // http://lxr.mozilla.org/seamonkey/source/netwerk/protocol/http/src/nsHttpRespo
nseHead.cpp |
7 // The rules for parsing content-types were also borrowed from Firefox: | 7 // The rules for parsing content-types were also borrowed from Firefox: |
8 // http://lxr.mozilla.org/mozilla/source/netwerk/base/src/nsURLHelper.cpp#834 | 8 // http://lxr.mozilla.org/mozilla/source/netwerk/base/src/nsURLHelper.cpp#834 |
9 | 9 |
10 #include "net/http/http_response_headers.h" | 10 #include "net/http/http_response_headers.h" |
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910 | 910 |
911 // From RFC 2616 section 13.2.4: | 911 // From RFC 2616 section 13.2.4: |
912 // | 912 // |
913 // The calculation to determine if a response has expired is quite simple: | 913 // The calculation to determine if a response has expired is quite simple: |
914 // | 914 // |
915 // response_is_fresh = (freshness_lifetime > current_age) | 915 // response_is_fresh = (freshness_lifetime > current_age) |
916 // | 916 // |
917 // Of course, there are other factors that can force a response to always be | 917 // Of course, there are other factors that can force a response to always be |
918 // validated or re-fetched. | 918 // validated or re-fetched. |
919 // | 919 // |
920 // From RFC 5861 section 3, a stale response may be used while revalidation is | 920 bool HttpResponseHeaders::RequiresValidation(const Time& request_time, |
921 // performed in the background if | 921 const Time& response_time, |
922 // | 922 const Time& current_time) const { |
923 // freshness_lifetime + stale_while_revalidate > current_age | |
924 // | |
925 ValidationType HttpResponseHeaders::RequiresValidation( | |
926 const Time& request_time, | |
927 const Time& response_time, | |
928 const Time& current_time) const { | |
929 FreshnessLifetimes lifetimes = GetFreshnessLifetimes(response_time); | 923 FreshnessLifetimes lifetimes = GetFreshnessLifetimes(response_time); |
930 if (lifetimes.freshness.is_zero() && lifetimes.staleness.is_zero()) | 924 if (lifetimes.freshness.is_zero()) |
931 return VALIDATION_SYNCHRONOUS; | 925 return true; |
932 | 926 return lifetimes.freshness <= |
933 TimeDelta age = GetCurrentAge(request_time, response_time, current_time); | 927 GetCurrentAge(request_time, response_time, current_time); |
934 | |
935 if (lifetimes.freshness > age) | |
936 return VALIDATION_NONE; | |
937 | |
938 if (lifetimes.freshness + lifetimes.staleness > age) | |
939 return VALIDATION_ASYNCHRONOUS; | |
940 | |
941 return VALIDATION_SYNCHRONOUS; | |
942 } | 928 } |
943 | 929 |
944 // From RFC 2616 section 13.2.4: | 930 // From RFC 2616 section 13.2.4: |
945 // | 931 // |
946 // The max-age directive takes priority over Expires, so if max-age is present | 932 // The max-age directive takes priority over Expires, so if max-age is present |
947 // in a response, the calculation is simply: | 933 // in a response, the calculation is simply: |
948 // | 934 // |
949 // freshness_lifetime = max_age_value | 935 // freshness_lifetime = max_age_value |
950 // | 936 // |
951 // Otherwise, if Expires is present in the response, the calculation is: | 937 // Otherwise, if Expires is present in the response, the calculation is: |
952 // | 938 // |
953 // freshness_lifetime = expires_value - date_value | 939 // freshness_lifetime = expires_value - date_value |
954 // | 940 // |
955 // Note that neither of these calculations is vulnerable to clock skew, since | 941 // Note that neither of these calculations is vulnerable to clock skew, since |
956 // all of the information comes from the origin server. | 942 // all of the information comes from the origin server. |
957 // | 943 // |
958 // Also, if the response does have a Last-Modified time, the heuristic | 944 // Also, if the response does have a Last-Modified time, the heuristic |
959 // expiration value SHOULD be no more than some fraction of the interval since | 945 // expiration value SHOULD be no more than some fraction of the interval since |
960 // that time. A typical setting of this fraction might be 10%: | 946 // that time. A typical setting of this fraction might be 10%: |
961 // | 947 // |
962 // freshness_lifetime = (date_value - last_modified_value) * 0.10 | 948 // freshness_lifetime = (date_value - last_modified_value) * 0.10 |
963 // | 949 // |
964 // If the stale-while-revalidate directive is present, then it is used to set | |
965 // the |staleness| time, unless it overridden by another directive. | |
966 // | |
967 HttpResponseHeaders::FreshnessLifetimes | 950 HttpResponseHeaders::FreshnessLifetimes |
968 HttpResponseHeaders::GetFreshnessLifetimes(const Time& response_time) const { | 951 HttpResponseHeaders::GetFreshnessLifetimes(const Time& response_time) const { |
969 FreshnessLifetimes lifetimes; | 952 FreshnessLifetimes lifetimes; |
970 // Check for headers that force a response to never be fresh. For backwards | 953 // Check for headers that force a response to never be fresh. For backwards |
971 // compat, we treat "Pragma: no-cache" as a synonym for "Cache-Control: | 954 // compat, we treat "Pragma: no-cache" as a synonym for "Cache-Control: |
972 // no-cache" even though RFC 2616 does not specify it. | 955 // no-cache" even though RFC 2616 does not specify it. |
973 if (HasHeaderValue("cache-control", "no-cache") || | 956 if (HasHeaderValue("cache-control", "no-cache") || |
974 HasHeaderValue("cache-control", "no-store") || | 957 HasHeaderValue("cache-control", "no-store") || |
975 HasHeaderValue("pragma", "no-cache") || | 958 HasHeaderValue("pragma", "no-cache") || |
976 // Vary: * is never usable: see RFC 2616 section 13.6. | 959 // Vary: * is never usable: see RFC 2616 section 13.6. |
977 HasHeaderValue("vary", "*")) { | 960 HasHeaderValue("vary", "*")) { |
978 return lifetimes; | 961 return lifetimes; |
979 } | 962 } |
980 | 963 |
981 // Cache-Control directive must_revalidate overrides stale-while-revalidate. | |
982 bool must_revalidate = HasHeaderValue("cache-control", "must-revalidate"); | |
983 | |
984 if (must_revalidate || !GetStaleWhileRevalidateValue(&lifetimes.staleness)) { | |
985 DCHECK_EQ(TimeDelta(), lifetimes.staleness); | |
986 } | |
987 | |
988 // NOTE: "Cache-Control: max-age" overrides Expires, so we only check the | 964 // NOTE: "Cache-Control: max-age" overrides Expires, so we only check the |
989 // Expires header after checking for max-age in GetFreshnessLifetimes. This | 965 // Expires header after checking for max-age in GetFreshnessLifetimes. This |
990 // is important since "Expires: <date in the past>" means not fresh, but | 966 // is important since "Expires: <date in the past>" means not fresh, but |
991 // it should not trump a max-age value. | 967 // it should not trump a max-age value. |
992 if (GetMaxAgeValue(&lifetimes.freshness)) | 968 if (GetMaxAgeValue(&lifetimes.freshness)) |
993 return lifetimes; | 969 return lifetimes; |
994 | 970 |
995 // If there is no Date header, then assume that the server response was | 971 // If there is no Date header, then assume that the server response was |
996 // generated at the time when we received the response. | 972 // generated at the time when we received the response. |
997 Time date_value; | 973 Time date_value; |
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1028 // a cache, that cache MUST NOT use the entry after it becomes stale to | 1004 // a cache, that cache MUST NOT use the entry after it becomes stale to |
1029 // respond to a subsequent request without first revalidating it with the | 1005 // respond to a subsequent request without first revalidating it with the |
1030 // origin server. (I.e., the cache MUST do an end-to-end revalidation every | 1006 // origin server. (I.e., the cache MUST do an end-to-end revalidation every |
1031 // time, if, based solely on the origin server's Expires or max-age value, | 1007 // time, if, based solely on the origin server's Expires or max-age value, |
1032 // the cached response is stale.) | 1008 // the cached response is stale.) |
1033 // | 1009 // |
1034 // https://datatracker.ietf.org/doc/draft-reschke-http-status-308/ is an | 1010 // https://datatracker.ietf.org/doc/draft-reschke-http-status-308/ is an |
1035 // experimental RFC that adds 308 permanent redirect as well, for which "any | 1011 // experimental RFC that adds 308 permanent redirect as well, for which "any |
1036 // future references ... SHOULD use one of the returned URIs." | 1012 // future references ... SHOULD use one of the returned URIs." |
1037 if ((response_code_ == 200 || response_code_ == 203 || | 1013 if ((response_code_ == 200 || response_code_ == 203 || |
1038 response_code_ == 206) && !must_revalidate) { | 1014 response_code_ == 206) && |
| 1015 !HasHeaderValue("cache-control", "must-revalidate")) { |
1039 // TODO(darin): Implement a smarter heuristic. | 1016 // TODO(darin): Implement a smarter heuristic. |
1040 Time last_modified_value; | 1017 Time last_modified_value; |
1041 if (GetLastModifiedValue(&last_modified_value)) { | 1018 if (GetLastModifiedValue(&last_modified_value)) { |
1042 // The last-modified value can be a date in the future! | 1019 // The last-modified value can be a date in the future! |
1043 if (last_modified_value <= date_value) { | 1020 if (last_modified_value <= date_value) { |
1044 lifetimes.freshness = (date_value - last_modified_value) / 10; | 1021 lifetimes.freshness = (date_value - last_modified_value) / 10; |
1045 return lifetimes; | 1022 return lifetimes; |
1046 } | 1023 } |
1047 } | 1024 } |
1048 } | 1025 } |
1049 | 1026 |
1050 // These responses are implicitly fresh (unless otherwise overruled): | 1027 // These responses are implicitly fresh (unless otherwise overruled): |
1051 if (response_code_ == 300 || response_code_ == 301 || response_code_ == 308 || | 1028 if (response_code_ == 300 || response_code_ == 301 || response_code_ == 308 || |
1052 response_code_ == 410) { | 1029 response_code_ == 410) { |
1053 lifetimes.freshness = TimeDelta::Max(); | 1030 lifetimes.freshness = TimeDelta::Max(); |
1054 lifetimes.staleness = TimeDelta(); // It should never be stale. | |
1055 return lifetimes; | 1031 return lifetimes; |
1056 } | 1032 } |
1057 | 1033 |
1058 // Our heuristic freshness estimate for this resource is 0 seconds, in | 1034 // Our heuristic freshness estimate for this resource is 0 seconds, in |
1059 // accordance with common browser behaviour. However, stale-while-revalidate | 1035 // accordance with common browser behaviour. |
1060 // may still apply. | |
1061 DCHECK_EQ(TimeDelta(), lifetimes.freshness); | 1036 DCHECK_EQ(TimeDelta(), lifetimes.freshness); |
1062 return lifetimes; | 1037 return lifetimes; |
1063 } | 1038 } |
1064 | 1039 |
1065 // From RFC 7234 section 4.2.3: | 1040 // From RFC 7234 section 4.2.3: |
1066 // | 1041 // |
1067 // The following data is used for the age calculation: | 1042 // The following data is used for the age calculation: |
1068 // | 1043 // |
1069 // age_value | 1044 // age_value |
1070 // | 1045 // |
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1161 } | 1136 } |
1162 | 1137 |
1163 bool HttpResponseHeaders::GetLastModifiedValue(Time* result) const { | 1138 bool HttpResponseHeaders::GetLastModifiedValue(Time* result) const { |
1164 return GetTimeValuedHeader("Last-Modified", result); | 1139 return GetTimeValuedHeader("Last-Modified", result); |
1165 } | 1140 } |
1166 | 1141 |
1167 bool HttpResponseHeaders::GetExpiresValue(Time* result) const { | 1142 bool HttpResponseHeaders::GetExpiresValue(Time* result) const { |
1168 return GetTimeValuedHeader("Expires", result); | 1143 return GetTimeValuedHeader("Expires", result); |
1169 } | 1144 } |
1170 | 1145 |
1171 bool HttpResponseHeaders::GetStaleWhileRevalidateValue( | |
1172 TimeDelta* result) const { | |
1173 return GetCacheControlDirective("stale-while-revalidate", result); | |
1174 } | |
1175 | |
1176 bool HttpResponseHeaders::GetTimeValuedHeader(const std::string& name, | 1146 bool HttpResponseHeaders::GetTimeValuedHeader(const std::string& name, |
1177 Time* result) const { | 1147 Time* result) const { |
1178 std::string value; | 1148 std::string value; |
1179 if (!EnumerateHeader(nullptr, name, &value)) | 1149 if (!EnumerateHeader(nullptr, name, &value)) |
1180 return false; | 1150 return false; |
1181 | 1151 |
1182 // When parsing HTTP dates it's beneficial to default to GMT because: | 1152 // When parsing HTTP dates it's beneficial to default to GMT because: |
1183 // 1. RFC2616 3.3.1 says times should always be specified in GMT | 1153 // 1. RFC2616 3.3.1 says times should always be specified in GMT |
1184 // 2. Only counter-example incorrectly appended "UTC" (crbug.com/153759) | 1154 // 2. Only counter-example incorrectly appended "UTC" (crbug.com/153759) |
1185 // 3. When adjusting cookie expiration times for clock skew | 1155 // 3. When adjusting cookie expiration times for clock skew |
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1346 return true; | 1316 return true; |
1347 } | 1317 } |
1348 | 1318 |
1349 bool HttpResponseHeaders::IsChunkEncoded() const { | 1319 bool HttpResponseHeaders::IsChunkEncoded() const { |
1350 // Ignore spurious chunked responses from HTTP/1.0 servers and proxies. | 1320 // Ignore spurious chunked responses from HTTP/1.0 servers and proxies. |
1351 return GetHttpVersion() >= HttpVersion(1, 1) && | 1321 return GetHttpVersion() >= HttpVersion(1, 1) && |
1352 HasHeaderValue("Transfer-Encoding", "chunked"); | 1322 HasHeaderValue("Transfer-Encoding", "chunked"); |
1353 } | 1323 } |
1354 | 1324 |
1355 } // namespace net | 1325 } // namespace net |
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