Description of problem:

dnf continues to download a package that has a partial -- locally broken --download.

dnf notices that the final checksum is wrong, so it starts a new download.  Good.

dnf restarts from the partially downloaded package, instead of from scratch.  The partial download is, however, broken, so every download from now on will result in a broken checksum.

example:

wine-core in fedora 21 was recently updated.  from 'dnf upgrade'.  Notice that dnf keeps restarting wine-core at 92% instead of deleting the broken partial download.  I've had this with other packages too.

.....
.....
[SKIPPED] xscreensaver-extras-base-5.32-3.fc21.x86_64.rpm: Already downloaded                                                                                               
[SKIPPED] xscreensaver-gl-base-5.32-3.fc21.x86_64.rpm: Already downloaded                                                                                                   
[SKIPPED] zeromq3-3.2.4-4.fc21.x86_64.rpm: Already downloaded                                                                                                               
[MIRROR] wine-core-1.7.33-1.fc21.x86_64.rpm: Downloading successfull, but checksum doesn't match. Expected: 25d806a49644c11c553d10d77d7425255e808ce0ebb1f26d8afb5ef5e363f6ce(sha256) 
[MIRROR] wine-core-1.7.33-1.fc21.x86_64.rpm: Downloading successfull, but checksum doesn't match. Expected: 25d806a49644c11c553d10d77d7425255e808ce0ebb1f26d8afb5ef5e363f6ce(sha256) 
[MIRROR] wine-core-1.7.33-1.fc21.x86_64.rpm: Downloading successfull, but checksum doesn't match. Expected: 25d806a49644c11c553d10d77d7425255e808ce0ebb1f26d8afb5ef5e363f6ce(sha256) 
[MIRROR] wine-core-1.7.33-1.fc21.x86_64.rpm: Downloading successfull, but checksum doesn't match. Expected: 25d806a49644c11c553d10d77d7425255e808ce0ebb1f26d8afb5ef5e363f6ce(sha256) 
[MIRROR] wine-core-1.7.33-1.fc21.x86_64.rpm: Downloading successfull, but checksum doesn't match. Expected: 25d806a49644c11c553d10d77d7425255e808ce0ebb1f26d8afb5ef5e363f6ce(sha256) 
[MIRROR] wine-core-1.7.33-1.fc21.x86_64.rpm: Downloading successfull, but checksum doesn't match. Expected: 25d806a49644c11c553d10d77d7425255e808ce0ebb1f26d8afb5ef5e363f6ce(sha256) 
[MIRROR] wine-core-1.7.33-1.fc21.x86_64.rpm: Downloading successfull, but checksum doesn't match. Expected: 25d806a49644c11c553d10d77d7425255e808ce0ebb1f26d8afb5ef5e363f6ce(sha256) 
[MIRROR] wine-core-1.7.33-1.fc21.x86_64.rpm: Downloading successfull, but checksum doesn't match. Expected: 25d806a49644c11c553d10d77d7425255e808ce0ebb1f26d8afb5ef5e363f6ce(sha256) 
(139/139): wine-core-1.7.33-1.fc21.x86_64.rpm                       92% [=============================================================     ] 1.1 MB/s | 250 MB     00:17 ETA


Version-Release number of selected component (if applicable):

dnf-0.6.3-2.fc21.noarch


How reproducible:

You'll need an interrupted network download while upgrading or installing a package.  Either interrupt the network, or suspend or shutdown while a download is busy.

the filesystem for /var/cache/ is ext4.


Steps to Reproduce:
1. start installing a package (a large one is easier)
2. unplug your network cable
3. wait a few minutes for dnf to die
4. replug your network cable
5. restart dnf


Actual results:

dnf is stuck in an infinite loop.


Expected results:

dnf notices the infinite loop, and eventually nukes the partial download and restarts from byte 0.

the correct solution for me was:
rm /var/cache/dnf/x86_64/21/updates/packages/wine-core-1.7.30-1.fc21_1.7.33-1.fc21.x86_64.drpm  /var/cache/dnf/x86_64/21/updates/packages/wine-core-1.7.33-1.fc21.x86_64.rpm



Additional info:

the worst case final result is that no security updates happen.  there is no notification that dnf is stuck.