Bug 1051567 - Make sure we resend file descriptors for the first chun…

…k of a message. r=billm

Check if the buffers iterator was never consumed. This is a regression
introduced when converting ipc to use BufferList in bug 1262671.

MozReview-Commit-ID: LWAoVlI5CKJ

ipc/chromium/src/chrome/common/ipc_channel_posix.cc

@@ -579,7 +579,12 @@ bool Channel::ChannelImpl::ProcessOutgoingMessages() {
         int[FileDescriptorSet::MAX_DESCRIPTORS_PER_MESSAGE]));
     char buf[tmp];
 
-    if (partial_write_iter_.isNothing() &&
+    if (partial_write_iter_.isNothing()) {
+      Pickle::BufferList::IterImpl iter(msg->Buffers());
+      partial_write_iter_.emplace(iter);
+    }
+
+    if (partial_write_iter_.value().Data() == msg->Buffers().Start() &&
         !msg->file_descriptor_set()->empty()) {
       // This is the first chunk of a message which has descriptors to send
       struct cmsghdr *cmsg;
@@ -611,11 +616,6 @@ bool Channel::ChannelImpl::ProcessOutgoingMessages() {
     size_t iov_count = 0;
     size_t amt_to_write = 0;
 
-    if (partial_write_iter_.isNothing()) {
-      Pickle::BufferList::IterImpl iter(msg->Buffers());
-      partial_write_iter_.emplace(iter);
-    }
-
     // How much of this message have we written so far?
     Pickle::BufferList::IterImpl iter = partial_write_iter_.value();
 

mfbt/BufferList.h

@@ -228,6 +228,7 @@ class BufferList : private AllocPolicy
 
   // Special convenience method that returns Iter().Data().
   char* Start() { return mSegments[0].mData; }
+  const char* Start() const { return mSegments[0].mData; }
 
   IterImpl Iter() const { return IterImpl(*this); }