[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [3.15-rc3] Bisected: xen-netback mangles packets between two guests on a bridge since merge of "TX grant mapping with SKBTX_DEV_ZEROCOPY instead of copy" series.
Wednesday, April 30, 2014, 10:53:39 PM, you wrote: > On 30/04/14 11:45, Sander Eikelenboom wrote: >> Hi Zoltan, >> >> Your series "TX grant mapping with SKBTX_DEV_ZEROCOPY instead of copy", >> merged into mainline with merge commit >> 4caeccb4de76440e433a15009636e77d003eb3d6, >> seem to introduce a subtle bug on network traffic between 2 guests on a >> bridge on the same host. >> I have one guest running apache as webdav server with SSL and another guest >> that is using that is uploading large files to that webdav server. >> Small requests (some get's and propfind's) seem to work ok, but when the >> bulk uploading begins it fails with: >> >> Attempt 1 failed. SSLError: [Errno 1] _ssl.c:1415: error:140943FC:SSL >> routines:SSL3_READ_BYTES:sslv3 alert bad record mac >> Attempt 2 failed. SSLError: [Errno 1] _ssl.c:1415: error:140943FC:SSL >> routines:SSL3_READ_BYTES:sslv3 alert bad record mac >> Attempt 3 failed. SSLError: [Errno 1] _ssl.c:1415: error:140943FC:SSL >> routines:SSL3_READ_BYTES:sslv3 alert bad record mac >> Attempt 4 failed. SSLError: [Errno 1] _ssl.c:1415: error:140943FC:SSL >> routines:SSL3_READ_BYTES:sslv3 alert bad record mac >> >> So some how large (probably fragmented) packets can get mangled when from >> guest to guest on the same host. >> I don't see this with clients that upload large files from external sources. >> Probably if SSL wasn't complaining it would probably be unnoticed for longer >> and doing some silent corruption. >> >> I first blamed openssl, since it started around all the latest openssl >> mayhem and updates, but it turns out it is all xen-netback related again. >> >> Since these commits break bisectabillity: >> - 1bb332af4cd889e4b64dacbf4a793ceb3a70445d (note in commit message && >> kernel panic) >> - 62bad3199a4c20505fc36c169deef20b25e17c5f (kernel panic) >> i stopped bisecting at this point. >> >> The upside is .. it's 100% reproduceable :-) > That's good :) Can you take tcpdump captures along the way (sending > guest, dom0, receiving guest), and try to work out which packets are > different, and where? Although taking captures in Dom0 might change your > result, as it triggers the pages to be copied and unmapped before they > reach their target. > Thanks, > Zoli Hrrmm that sounds like a lot of data and a lot of work .. how ever .. could it be just a type and would the following make sense ? diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index 7666540..abeea10 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -1366,7 +1366,7 @@ static int xenvif_handle_frag_list(struct xenvif *vif, struct sk_buff *skb) xenvif_fill_frags(vif, nskb); /* Subtract frags size, we will correct it later */ - skb->truesize -= skb->data_len; + skb->truesize -= nskb->data_len; skb->len += nskb->len; skb->data_len += nskb->len; -- Sander >> >> On a sidenote: >> Although DaveM seems to prefer patches, it would probably be nice to >> have larger patchsets like this one in a git tree somewhere, >> for more easy isolated applying to stable kernels, that would improve >> testing and bisecting things. >> For example the kernel xen.git tree makes it very easy to pull the >> devel branches to current stable .. >> and even test those *isolated* and *before* the merge window, that >> greatly reduces the effort of testing and if anything is wrong .. in >> bisecting things. >> >> Another point would be: what *correctness* testing is actually done on >> the xen-net* patches ? >> As i suspect this is again about fragmented packets .. that doesn't >> seem to be included in any test case while it actually seems to be a case >> which is hard to get right... >> >> -- >> Sander >> >> The bisection log: >> git bisect start >> # bad: [cd6362befe4cc7bf589a5236d2a780af2d47bcc9] Merge >> git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next >> git bisect bad cd6362befe4cc7bf589a5236d2a780af2d47bcc9 >> # good: [df69491b7d1550137507a7eb5f2fc5dce0c1e534] Merge branch 'xen-netback' >> git bisect good df69491b7d1550137507a7eb5f2fc5dce0c1e534 >> # good: [c12e69c6aaf785fd307d05cb6f36ca0e7577ead7] Merge tag >> 'staging-3.15-rc1' of >> git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging >> git bisect good c12e69c6aaf785fd307d05cb6f36ca0e7577ead7 >> # bad: [49c0ca17ee8dd3530f688052d4eb2ae6d3e55119] Merge branch 'master' of >> git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-next into >> for-davem >> git bisect bad 49c0ca17ee8dd3530f688052d4eb2ae6d3e55119 >> # good: [370c5acef0326db3e8c10d42b941289c9c887a4a] Merge branch >> 'for-upstream' of >> git://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth-next >> git bisect good 370c5acef0326db3e8c10d42b941289c9c887a4a >> # good: [ec5709403e6893acb4f7ca40514ebd29c3116836] net/mlx4_en: Use union >> for BlueFlame WQE >> git bisect good ec5709403e6893acb4f7ca40514ebd29c3116836 >> # bad: [69bfb110fd58185df99a7dbe92a14c0d7ada764f] i40e: cleanup strings >> git bisect bad 69bfb110fd58185df99a7dbe92a14c0d7ada764f >> # bad: [aeb12c5ef7cb08d879af22fc0a56cab9e70689ea] gianfar: Separate out the >> Tx interrupt handling (Tx NAPI) >> git bisect bad aeb12c5ef7cb08d879af22fc0a56cab9e70689ea >> # bad: [389400428953bb002b173fa07d16d7a6f120843f] Merge tag >> 'rxrpc-devel-20140304' of >> git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs >> git bisect bad 389400428953bb002b173fa07d16d7a6f120843f >> # good: [5a8a1ab74dce1b50fe27745df477c502aec987eb] be2net: do external >> loopback test only when it is requested >> git bisect good 5a8a1ab74dce1b50fe27745df477c502aec987eb >> # skip: [1bb332af4cd889e4b64dacbf4a793ceb3a70445d] xen-netback: Add stat >> counters for zerocopy >> git bisect skip 1bb332af4cd889e4b64dacbf4a793ceb3a70445d >> # skip: [e86800f9201d35b6b2aac1583a9bf9e3a0b0c70d] Merge branch '6lowpan' >> git bisect skip e86800f9201d35b6b2aac1583a9bf9e3a0b0c70d >> # good: [31c70d5956fc3d1abf83e9ab5e1d8237dea59498] l2tp: keep original skb >> ownership >> git bisect good 31c70d5956fc3d1abf83e9ab5e1d8237dea59498 >> >> _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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