internal static bool ContentIsNotModified(ResponseCachingContext context)
{
var cachedResponseHeaders = context.CachedResponseHeaders;
var ifNoneMatchHeader = context.HttpContext.Request.Headers[HeaderNames.IfNoneMatch];
if (!StringValues.IsNullOrEmpty(ifNoneMatchHeader))
{
if (ifNoneMatchHeader.Count == 1 && StringSegment.Equals(ifNoneMatchHeader[0], EntityTagHeaderValue.Any.Tag, StringComparison.OrdinalIgnoreCase))
{
context.Logger.NotModifiedIfNoneMatchStar();
return(true);
}
EntityTagHeaderValue eTag;
IList <EntityTagHeaderValue> ifNoneMatchEtags;
if (!StringValues.IsNullOrEmpty(cachedResponseHeaders[HeaderNames.ETag]) &&
EntityTagHeaderValue.TryParse(cachedResponseHeaders[HeaderNames.ETag].ToString(), out eTag) &&
EntityTagHeaderValue.TryParseList(ifNoneMatchHeader, out ifNoneMatchEtags))
{
for (var i = 0; i < ifNoneMatchEtags.Count; i++)
{
var requestETag = ifNoneMatchEtags[i];
if (eTag.Compare(requestETag, useStrongComparison: false))
{
context.Logger.NotModifiedIfNoneMatchMatched(requestETag);
return(true);
}
}
}
}
else
{
var ifModifiedSince = context.HttpContext.Request.Headers[HeaderNames.IfModifiedSince];
if (!StringValues.IsNullOrEmpty(ifModifiedSince))
{
DateTimeOffset modified;
if (!HeaderUtilities.TryParseDate(cachedResponseHeaders[HeaderNames.LastModified].ToString(), out modified) &&
!HeaderUtilities.TryParseDate(cachedResponseHeaders[HeaderNames.Date].ToString(), out modified))
{
return(false);
}
DateTimeOffset modifiedSince;
if (HeaderUtilities.TryParseDate(ifModifiedSince.ToString(), out modifiedSince) &&
modified <= modifiedSince)
{
context.Logger.NotModifiedIfModifiedSinceSatisfied(modified, modifiedSince);
return(true);
}
}
}
return(false);
}
private static TimeSpan?GetCacheTtl(RequestContext requestContext)
{
var response = requestContext.Response;
// Only consider kernel-mode caching if the Cache-Control response header is present.
var cacheControlHeader = response.Headers[HeaderNames.CacheControl];
if (string.IsNullOrEmpty(cacheControlHeader))
{
return(null);
}
// Before we check the header value, check for the existence of other headers which would
// make us *not* want to cache the response.
if (response.Headers.ContainsKey(HeaderNames.SetCookie) ||
response.Headers.ContainsKey(HeaderNames.Vary) ||
response.Headers.ContainsKey(HeaderNames.Pragma))
{
return(null);
}
// We require 'public' and 's-max-age' or 'max-age' or the Expires header.
CacheControlHeaderValue cacheControl;
if (CacheControlHeaderValue.TryParse(cacheControlHeader, out cacheControl) && cacheControl.Public)
{
if (cacheControl.SharedMaxAge.HasValue)
{
return(cacheControl.SharedMaxAge);
}
else if (cacheControl.MaxAge.HasValue)
{
return(cacheControl.MaxAge);
}
DateTimeOffset expirationDate;
if (HeaderUtilities.TryParseDate(response.Headers[HeaderNames.Expires], out expirationDate))
{
var expiresOffset = expirationDate - DateTimeOffset.UtcNow;
if (expiresOffset > TimeSpan.Zero)
{
return(expiresOffset);
}
}
}
return(null);
}
public virtual bool IsCachedEntryFresh(ResponseCachingContext context)
{
var age = context.CachedEntryAge !.Value;
var cachedCacheControlHeaders = context.CachedResponseHeaders.CacheControl;
var requestCacheControlHeaders = context.HttpContext.Request.Headers.CacheControl;
// Add min-fresh requirements
if (HeaderUtilities.TryParseSeconds(requestCacheControlHeaders, CacheControlHeaderValue.MinFreshString, out var minFresh))
{
age += minFresh.Value;
context.Logger.ExpirationMinFreshAdded(minFresh.Value);
}
// Validate shared max age, this overrides any max age settings for shared caches
TimeSpan?cachedSharedMaxAge;
HeaderUtilities.TryParseSeconds(cachedCacheControlHeaders, CacheControlHeaderValue.SharedMaxAgeString, out cachedSharedMaxAge);
if (age >= cachedSharedMaxAge)
{
// shared max age implies must revalidate
context.Logger.ExpirationSharedMaxAgeExceeded(age, cachedSharedMaxAge.Value);
return(false);
}
else if (!cachedSharedMaxAge.HasValue)
{
TimeSpan?requestMaxAge;
HeaderUtilities.TryParseSeconds(requestCacheControlHeaders, CacheControlHeaderValue.MaxAgeString, out requestMaxAge);
TimeSpan?cachedMaxAge;
HeaderUtilities.TryParseSeconds(cachedCacheControlHeaders, CacheControlHeaderValue.MaxAgeString, out cachedMaxAge);
var lowestMaxAge = cachedMaxAge < requestMaxAge ? cachedMaxAge : requestMaxAge ?? cachedMaxAge;
// Validate max age
if (age >= lowestMaxAge)
{
// Must revalidate or proxy revalidate
if (HeaderUtilities.ContainsCacheDirective(cachedCacheControlHeaders, CacheControlHeaderValue.MustRevalidateString) ||
HeaderUtilities.ContainsCacheDirective(cachedCacheControlHeaders, CacheControlHeaderValue.ProxyRevalidateString))
{
context.Logger.ExpirationMustRevalidate(age, lowestMaxAge.Value);
return(false);
}
TimeSpan?requestMaxStale;
var maxStaleExist = HeaderUtilities.ContainsCacheDirective(requestCacheControlHeaders, CacheControlHeaderValue.MaxStaleString);
HeaderUtilities.TryParseSeconds(requestCacheControlHeaders, CacheControlHeaderValue.MaxStaleString, out requestMaxStale);
// Request allows stale values with no age limit
if (maxStaleExist && !requestMaxStale.HasValue)
{
context.Logger.ExpirationInfiniteMaxStaleSatisfied(age, lowestMaxAge.Value);
return(true);
}
// Request allows stale values with age limit
if (requestMaxStale.HasValue && age - lowestMaxAge < requestMaxStale)
{
context.Logger.ExpirationMaxStaleSatisfied(age, lowestMaxAge.Value, requestMaxStale.Value);
return(true);
}
context.Logger.ExpirationMaxAgeExceeded(age, lowestMaxAge.Value);
return(false);
}
else if (!cachedMaxAge.HasValue && !requestMaxAge.HasValue)
{
// Validate expiration
DateTimeOffset expires;
if (HeaderUtilities.TryParseDate(context.CachedResponseHeaders.Expires.ToString(), out expires) &&
context.ResponseTime !.Value >= expires)
{
context.Logger.ExpirationExpiresExceeded(context.ResponseTime.Value, expires);
return(false);
}
}
}
return(true);
}
public void TryParse_SetOfInvalidValueStrings_ReturnsFalse(string input)
{
Assert.False(HeaderUtilities.TryParseDate(input, out var result));
Assert.Equal(new DateTimeOffset(), result);
}
