Noticed this in my code review: https://petertodd.org/2016/segwit-consensus-critical-code-review#peer-to-peer-networking

Basically it looks like an attacker may be able to send nodes transactions with malleated witness data, which we don't consistently mark as possibly corrupted in AcceptToMemoryPool(). Result would be those txids being added to recentRejects, messing up propagation.

That said, I haven't actually tested this yet; about to go off to a conference, so if someone else wants to confirm for me that'd be much appreciated! Or if I'm wrong you're welcome to all laugh at my expense. :)

CC: @sdaftuar @sipa 

{
        return &(*a) < &(*b);
    }
};
struct COrphanTx {
    CTransaction tx;
    NodeId fromPeer;
    int64_t nTimeExpire;
};
map<uint256, COrphanTx> mapOrphanTransactions GUARDED_BY(cs_main);
map<COutPoint, set<map<uint256, COrphanTx>::iterator, IteratorComparator>> mapOrphanTransactionsByPrev GUARDED_BY(cs_main);
void EraseOrphansFor(NodeId peer) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
/**
 * Returns true if there are nRequired or more blocks of minVersion or above
 * in the last Consensus::Params::nMajorityWindow blocks, starting at pstart and going backwards.
 */
static bool IsSuperMajority(int minVersion, const CBlockIndex* pstart, unsigned nRequired, const Consensus::Params& consensusParams);
static void CheckBlockIndex(const Consensus::Params& consensusParams);
CScript COINBASE_FLAGS;
const string strMessageMagic = "Bitcoin Signed Message:\n";
namespace {
    struct CBlockIndexWorkComparator
    {
        bool operator()(CBlockIndex *pa, CBlockIndex *pb) const {