From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: passt.top; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: passt.top; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=jRI0hNv3; dkim-atps=neutral Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by passt.top (Postfix) with ESMTP id D9B005A004C for ; Fri, 27 Sep 2024 15:49:55 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1727444994; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=G51zikJPvjJAP+mnzBOIG11GcGttXFt+0UBDeME94vg=; b=jRI0hNv3QJ/HHUwEREDX41i/tTUwFmvwXG2kpw0AcUizmRJetgyp7RXuvhyUF470kg4nzO jFkQEsTRiVREoKNgRDeqfW13ZPoqZKY7TVxOYRclqLQQGXNtGJHC+njAqE9EpDA8zKSH6f HvTLhQsEaW5cnt07lsA5z15y8gGvlL0= Received: from mail-wr1-f72.google.com (mail-wr1-f72.google.com [209.85.221.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-611-4yj9sIS6M02ckkSYzYHfkg-1; Fri, 27 Sep 2024 09:49:53 -0400 X-MC-Unique: 4yj9sIS6M02ckkSYzYHfkg-1 Received: by mail-wr1-f72.google.com with SMTP id ffacd0b85a97d-374beb23f35so1074699f8f.0 for ; Fri, 27 Sep 2024 06:49:53 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1727444992; x=1728049792; h=content-transfer-encoding:in-reply-to:autocrypt:from :content-language:references:cc:to:subject:user-agent:mime-version :date:message-id:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=G51zikJPvjJAP+mnzBOIG11GcGttXFt+0UBDeME94vg=; b=tHgdflJ4ttfJjfoOOMkS+0qZugUB1SyGoSj8mNYcwkl0xX31b6xkEpGQRSepzhj7vd AWBUVKkA1zfOEFERSCoQ+9LwbdB4DZwk5HpGj7vBhck68LXZEoV/TBKTDovMWpsD/8Nt hoPoRXEBWUWnmi2tq1+YuCjHKJXAJCruVUSPIh1rCd2klasMLPMr75YTn7W24/lwLADJ 0xVB/U3zMCMXBvAWgQO7RWCX7tRW1WT3eb6VBRYVPGcBjgp8OLl2pCqk3RtCsqXUFOHm LjnZOGDoiEzSkYt/jOR9HVV0PFaAsJllPTDaXdDA4q7YhbM5r9LiWCLmrVRW8AbKQHiA fl/Q== X-Gm-Message-State: AOJu0Ywg3kP3qXqiUFiP1+CNTc9x5QqjtUCwVyWKHvJZ7Q+KAy3iY3fd dm1HZFzT9QeAIFUbYFULIzMO/Ev4MhVK7DWBr6JeLO/QEQ2FxIROlLw6RyHc5sK9ZrjNVEdWMRq NA1fV1dZUs8yFzWwleTBkAdkm/s0F7V+nJNEnFWV7kyfmQNuQK57DfWeEEQ== X-Received: by 2002:a5d:4745:0:b0:37c:d1eb:5527 with SMTP id ffacd0b85a97d-37cd5a9e43emr1984356f8f.31.1727444992086; Fri, 27 Sep 2024 06:49:52 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHGcqZRpdWl+TtpPV0Z78kaAjdo+/aIJVkTAeQIRekrHCSF1MNSuppXBPSZb/6Cu6fXuzTuww== X-Received: by 2002:a5d:4745:0:b0:37c:d1eb:5527 with SMTP id ffacd0b85a97d-37cd5a9e43emr1984337f8f.31.1727444991522; Fri, 27 Sep 2024 06:49:51 -0700 (PDT) Received: from ?IPV6:2a01:e0a:e10:ef90:4c84:58cb:a1ef:8b78? ([2a01:e0a:e10:ef90:4c84:58cb:a1ef:8b78]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-37cd575c830sm2538264f8f.111.2024.09.27.06.49.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 27 Sep 2024 06:49:50 -0700 (PDT) Message-ID: <1ccee20e-fbb5-47ab-8a87-939e7c81ed54@redhat.com> Date: Fri, 27 Sep 2024 15:49:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/4] tcp: Update TCP checksum using an iovec array To: David Gibson References: <20240925081125.205974-1-lvivier@redhat.com> <20240925081125.205974-5-lvivier@redhat.com> From: Laurent Vivier Autocrypt: addr=lvivier@redhat.com; keydata= xsFNBFYFJhkBEAC2me7w2+RizYOKZM+vZCx69GTewOwqzHrrHSG07MUAxJ6AY29/+HYf6EY2 WoeuLWDmXE7A3oJoIsRecD6BXHTb0OYS20lS608anr3B0xn5g0BX7es9Mw+hV/pL+63EOCVm SUVTEQwbGQN62guOKnJJJfphbbv82glIC/Ei4Ky8BwZkUuXd7d5NFJKC9/GDrbWdj75cDNQx UZ9XXbXEKY9MHX83Uy7JFoiFDMOVHn55HnncflUncO0zDzY7CxFeQFwYRbsCXOUL9yBtqLer Ky8/yjBskIlNrp0uQSt9LMoMsdSjYLYhvk1StsNPg74+s4u0Q6z45+l8RAsgLw5OLtTa+ePM JyS7OIGNYxAX6eZk1+91a6tnqfyPcMbduxyBaYXn94HUG162BeuyBkbNoIDkB7pCByed1A7q q9/FbuTDwgVGVLYthYSfTtN0Y60OgNkWCMtFwKxRaXt1WFA5ceqinN/XkgA+vf2Ch72zBkJL RBIhfOPFv5f2Hkkj0MvsUXpOWaOjatiu0fpPo6Hw14UEpywke1zN4NKubApQOlNKZZC4hu6/ 8pv2t4HRi7s0K88jQYBRPObjrN5+owtI51xMaYzvPitHQ2053LmgsOdN9EKOqZeHAYG2SmRW LOxYWKX14YkZI5j/TXfKlTpwSMvXho+efN4kgFvFmP6WT+tPnwARAQABzSNMYXVyZW50IFZp dmllciA8bHZpdmllckByZWRoYXQuY29tPsLBeAQTAQIAIgUCVgVQgAIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AACgkQ8ww4vT8vvjwpgg//fSGy0Rs/t8cPFuzoY1cex4limJQfReLr SJXCANg9NOWy/bFK5wunj+h/RCFxIFhZcyXveurkBwYikDPUrBoBRoOJY/BHK0iZo7/WQkur 6H5losVZtrotmKOGnP/lJYZ3H6OWvXzdz8LL5hb3TvGOP68K8Bn8UsIaZJoeiKhaNR0sOJyI YYbgFQPWMHfVwHD/U+/gqRhD7apVysxv5by/pKDln1I5v0cRRH6hd8M8oXgKhF2+rAOL7gvh jEHSSWKUlMjC7YwwjSZmUkL+TQyE18e2XBk85X8Da3FznrLiHZFHQ/NzETYxRjnOzD7/kOVy gKD/o7asyWQVU65mh/ECrtjfhtCBSYmIIVkopoLaVJ/kEbVJQegT2P6NgERC/31kmTF69vn8 uQyW11Hk8tyubicByL3/XVBrq4jZdJW3cePNJbTNaT0d/bjMg5zCWHbMErUib2Nellnbg6bc 2HLDe0NLVPuRZhHUHM9hO/JNnHfvgiRQDh6loNOUnm9Iw2YiVgZNnT4soUehMZ7au8PwSl4I KYE4ulJ8RRiydN7fES3IZWmOPlyskp1QMQBD/w16o+lEtY6HSFEzsK3o0vuBRBVp2WKnssVH qeeV01ZHw0bvWKjxVNOksP98eJfWLfV9l9e7s6TaAeySKRRubtJ+21PRuYAxKsaueBfUE7ZT 7zfOwU0EVgUmGQEQALxSQRbl/QOnmssVDxWhHM5TGxl7oLNJms2zmBpcmlrIsn8nNz0rRyxT 460k2niaTwowSRK8KWVDeAW6ZAaWiYjLlTunoKwvF8vP3JyWpBz0diTxL5o+xpvy/Q6YU3BN efdq8Vy3rFsxgW7mMSrI/CxJ667y8ot5DVugeS2NyHfmZlPGE0Nsy7hlebS4liisXOrN3jFz asKyUws3VXek4V65lHwB23BVzsnFMn/bw/rPliqXGcwl8CoJu8dSyrCcd1Ibs0/Inq9S9+t0 VmWiQWfQkz4rvEeTQkp/VfgZ6z98JRW7S6l6eophoWs0/ZyRfOm+QVSqRfFZdxdP2PlGeIFM C3fXJgygXJkFPyWkVElr76JTbtSHsGWbt6xUlYHKXWo+xf9WgtLeby3cfSkEchACrxDrQpj+ Jt/JFP+q997dybkyZ5IoHWuPkn7uZGBrKIHmBunTco1+cKSuRiSCYpBIXZMHCzPgVDjk4viP brV9NwRkmaOxVvye0vctJeWvJ6KA7NoAURplIGCqkCRwg0MmLrfoZnK/gRqVJ/f6adhU1oo6 z4p2/z3PemA0C0ANatgHgBb90cd16AUxpdEQmOCmdNnNJF/3Zt3inzF+NFzHoM5Vwq6rc1JP jfC3oqRLJzqAEHBDjQFlqNR3IFCIAo4SYQRBdAHBCzkM4rWyRhuVABEBAAHCwV8EGAECAAkF AlYFJhkCGwwACgkQ8ww4vT8vvjwg9w//VQrcnVg3TsjEybxDEUBm8dBmnKqcnTBFmxN5FFtI WlEuY8+YMiWRykd8Ln9RJ/98/ghABHz9TN8TRo2b6WimV64FmlVn17Ri6FgFU3xNt9TTEChq AcNg88eYryKsYpFwegGpwUlaUaaGh1m9OrTzcQy+klVfZWaVJ9Nw0keoGRGb8j4XjVpL8+2x OhXKrM1fzzb8JtAuSbuzZSQPDwQEI5CKKxp7zf76J21YeRrEW4WDznPyVcDTa+tz++q2S/Bp P4W98bXCBIuQgs2m+OflERv5c3Ojldp04/S4NEjXEYRWdiCxN7ca5iPml5gLtuvhJMSy36gl U6IW9kn30IWuSoBpTkgV7rLUEhh9Ms82VWW/h2TxL8enfx40PrfbDtWwqRID3WY8jLrjKfTd R3LW8BnUDNkG+c4FzvvGUs8AvuqxxyHbXAfDx9o/jXfPHVRmJVhSmd+hC3mcQ+4iX5bBPBPM oDqSoLt5w9GoQQ6gDVP2ZjTWqwSRMLzNr37rJjZ1pt0DCMMTbiYIUcrhX8eveCJtY7NGWNyx FCRkhxRuGcpwPmRVDwOl39MB3iTsRighiMnijkbLXiKoJ5CDVvX5yicNqYJPKh5MFXN1bvsB kmYiStMRbrD0HoY1kx5/VozBtc70OU0EB8Wrv9hZD+Ofp0T3KOr1RUHvCZoLURfFhSQ= In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Message-ID-Hash: NAT6BSBMKRXJDKARSFBBML6KAE5EHEPG X-Message-ID-Hash: NAT6BSBMKRXJDKARSFBBML6KAE5EHEPG X-MailFrom: lvivier@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On 26/09/2024 03:45, David Gibson wrote: > On Wed, Sep 25, 2024 at 10:11:25AM +0200, Laurent Vivier wrote: >> TCP header and payload are supposed to be in the same buffer, >> and tcp_update_check_tcp4()/tcp_update_check_tcp6() compute >> the checksum from the base address of the header using the >> length of the IP payload. >> >> In the future (for vhost-user) we need to dispatch the TCP header and >> the TCP payload through several buffers. To be able to manage that, we >> provide an iovec array that points to the data of the TCP frame. >> We provide also an offset to be able to provide an array that contains >> the TCP frame embedded in an lower level frame, and this offset points >> to the TCP header inside the iovec array. >> >> Signed-off-by: Laurent Vivier >> --- >> >> Notes: >> v2: >> - s/payload_offset/l4offset/ >> - check memory address of the checksum (alignment, iovec boundaries) >> >> checksum.c | 1 - >> tcp.c | 116 ++++++++++++++++++++++++++++++++++++++++------------- >> 2 files changed, 88 insertions(+), 29 deletions(-) >> >> diff --git a/checksum.c b/checksum.c >> index 68ffaddb5bb0..4854c1937c39 100644 >> --- a/checksum.c >> +++ b/checksum.c >> @@ -503,7 +503,6 @@ uint16_t csum(const void *buf, size_t len, uint32_t init) >> * >> * Return: 16-bit folded, complemented checksum >> */ >> -/* cppcheck-suppress unusedFunction */ >> uint16_t csum_iov(const struct iovec *iov, size_t n, size_t offset, >> uint32_t init) >> { >> diff --git a/tcp.c b/tcp.c >> index c9472d905520..f0a6f7a507a7 100644 >> --- a/tcp.c >> +++ b/tcp.c >> @@ -755,36 +755,81 @@ static void tcp_sock_set_bufsize(const struct ctx *c, int s) >> } >> >> /** >> - * tcp_update_check_tcp4() - Update TCP checksum from stored one >> - * @iph: IPv4 header >> - * @bp: TCP header followed by TCP payload >> - */ >> -static void tcp_update_check_tcp4(const struct iphdr *iph, >> - struct tcp_payload_t *bp) >> + * tcp_update_check_tcp4() - Calculate TCP checksum for IPv6 > > Nit: s/IPv6/IPv4/ > >> + * @src: IPv4 source address >> + * @dst: IPv4 destination address >> + * @iov: Pointer to the array of IO vectors >> + * @iov_cnt: Length of the array >> + * @l4offset: IPv4 payload offset in the iovec array >> + */ >> +void tcp_update_check_tcp4(struct in_addr src, >> + struct in_addr dst, >> + const struct iovec *iov, int iov_cnt, >> + size_t l4offset) >> { >> - uint16_t l4len = ntohs(iph->tot_len) - sizeof(struct iphdr); >> - struct in_addr saddr = { .s_addr = iph->saddr }; >> - struct in_addr daddr = { .s_addr = iph->daddr }; >> - uint32_t sum = proto_ipv4_header_psum(l4len, IPPROTO_TCP, saddr, daddr); >> + size_t check_ofs; >> + __sum16 *check; >> + int check_idx; >> + uint32_t sum; >> + >> + sum = proto_ipv4_header_psum(iov_size(iov, iov_cnt) - l4offset, >> + IPPROTO_TCP, src, dst); > > Previously, we took the size from the IP header, which we'd previously > calculated. It seems a shame to replace that with a call to > iov_size() which will make another pass through the whole vector. > >> + >> + check_idx = iov_skip_bytes(iov, iov_cnt, >> + l4offset + offsetof(struct tcphdr, check), >> + &check_ofs); >> + >> + if (check_idx >= iov_cnt) >> + die("TCP4 buffer is too small"); >> + if (check_ofs + sizeof(*check) > iov[check_idx].iov_len) >> + die("TCP4 checksum field memory is not contiguous"); >> + >> + check = (__sum16 *)((char *)iov[check_idx].iov_base + check_ofs); > > Strictly speaking, it's UB to even *create* an improperly aligned > pointer, even if you never dereference it. So the alignment check > should go before casting to (__sum16 *). > >> - bp->th.check = 0; >> - bp->th.check = csum(bp, l4len, sum); >> + if ((uintptr_t)check & (__alignof__(*check) - 1)) >> + die("TCP4 checksum field is not correctly aligned in memory"); > > I really think it would be worth packaging this logic (skip_bytes + > contiguous check + alignment check + pointer cast) into another helper > (iov_field()?). I strongly suspect we'll have further use for it down > the line. > I'm addressing all your other comments but I don't really have the time to write a generic and clean function to do that. I prefer to duplicate the code for the moment, we will be able to cleanup this in the future. Thanks, Laurent