From 355e1aceac1dd05c4c7daf3420b09bd860fd169d Mon Sep 17 00:00:00 2001
From: David Kalnischkies <david@kalnischkies.de>
Date: Fri, 27 Oct 2017 19:09:45 +0200
Subject: implement fallback to alternative URIs for all items

For deb files we always supported falling back from one server to the
other if one failed to download the deb, but that was hardwired in the
handling of this specific item. Moving this alongside the retry
infrastructure we can implement it for all items and allow methods to
use this as well by providing additional URIs in a redirect.
---
 apt-pkg/acquire-worker.cc | 53 ++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 46 insertions(+), 7 deletions(-)

(limited to 'apt-pkg/acquire-worker.cc')

diff --git a/apt-pkg/acquire-worker.cc b/apt-pkg/acquire-worker.cc
index a763d9242..995750dea 100644
--- a/apt-pkg/acquire-worker.cc
+++ b/apt-pkg/acquire-worker.cc
@@ -211,6 +211,39 @@ static bool isDoomedItem(pkgAcquire::Item const * const Itm)
       return false;
    return TransItm->TransactionManager->State != pkgAcqTransactionItem::TransactionStarted;
 }
+static HashStringList GetHashesFromMessage(std::string const &Prefix, std::string const &Message)
+{
+   HashStringList hsl;
+   for (char const *const *type = HashString::SupportedHashes(); *type != NULL; ++type)
+   {
+      std::string const tagname = Prefix + *type + "-Hash";
+      std::string const hashsum = LookupTag(Message, tagname.c_str());
+      if (hashsum.empty() == false)
+	 hsl.push_back(HashString(*type, hashsum));
+   }
+   return hsl;
+}
+static void APT_NONNULL(3) ChangeSiteIsMirrorChange(std::string const &NewURI, pkgAcquire::ItemDesc &desc, pkgAcquire::Item *const Owner)
+{
+   if (URI::SiteOnly(NewURI) == URI::SiteOnly(desc.URI))
+      return;
+
+   auto const firstSpace = desc.Description.find(" ");
+   if (firstSpace != std::string::npos)
+   {
+      std::string const OldSite = desc.Description.substr(0, firstSpace);
+      if (likely(APT::String::Startswith(desc.URI, OldSite)))
+      {
+	 std::string const OldExtra = desc.URI.substr(OldSite.length() + 1);
+	 if (likely(APT::String::Endswith(NewURI, OldExtra)))
+	 {
+	    std::string const NewSite = NewURI.substr(0, NewURI.length() - OldExtra.length());
+	    Owner->UsedMirror = URI::ArchiveOnly(NewSite);
+	    desc.Description.replace(0, firstSpace, Owner->UsedMirror);
+	 }
+      }
+   }
+}
 bool pkgAcquire::Worker::RunMessages()
 {
    while (MessageQueue.empty() == false)
@@ -377,13 +410,7 @@ bool pkgAcquire::Worker::RunMessages()
 	       std::string const givenfilename = LookupTag(Message, "Filename");
 	       std::string const filename = givenfilename.empty() ? Itm->Owner->DestFile : givenfilename;
 	       // see if we got hashes to verify
-	       for (char const * const * type = HashString::SupportedHashes(); *type != NULL; ++type)
-	       {
-		  std::string const tagname = std::string(*type) + "-Hash";
-		  std::string const hashsum = LookupTag(Message, tagname.c_str());
-		  if (hashsum.empty() == false)
-		     ReceivedHashes.push_back(HashString(*type, hashsum));
-	       }
+	       ReceivedHashes = GetHashesFromMessage("", Message);
 	       // not all methods always sent Hashes our way
 	       if (ReceivedHashes.usable() == false)
 	       {
@@ -525,6 +552,7 @@ bool pkgAcquire::Worker::RunMessages()
 
 	    for (auto const Owner: ItmOwners)
 	    {
+	       std::string NewURI;
 	       if (errTransient == true && Config->LocalOnly == false && Owner->ModifyRetries() != 0)
 	       {
 		  --Owner->ModifyRetries();
@@ -535,6 +563,17 @@ bool pkgAcquire::Worker::RunMessages()
 		  if (isDoomedItem(Owner) == false)
 		     OwnerQ->Owner->Enqueue(SavedDesc);
 	       }
+	       else if (Owner->PopAlternativeURI(NewURI))
+	       {
+		  Owner->FailMessage(Message);
+		  auto &desc = Owner->GetItemDesc();
+		  if (Log != nullptr)
+		     Log->Fail(desc);
+		  ChangeSiteIsMirrorChange(NewURI, desc, Owner);
+		  desc.URI = NewURI;
+		  if (isDoomedItem(Owner) == false)
+		     OwnerQ->Owner->Enqueue(desc);
+	       }
 	       else
 	       {
 		  if (errAuthErr && Owner->GetExpectedHashes().empty() == false)
-- 
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