From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [IPv6:2a01:7e0:0:424::9]) by lore.proxmox.com (Postfix) with ESMTPS id 70FA11FF13F for ; Thu, 26 Feb 2026 13:04:30 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 639591E343; Thu, 26 Feb 2026 13:05:25 +0100 (CET) Message-ID: <9a29482f-8dde-40d5-b48d-c2808052332d@proxmox.com> Date: Thu, 26 Feb 2026 13:04:41 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH qemu-server v2 3/3] agent: file-read: Allow specifying byte offset to start reading at To: Markus Ebner , pve-devel@lists.proxmox.com References: <20260225112851.124188-1-info@ebner-markus.de> <20260225112851.124188-4-info@ebner-markus.de> Content-Language: en-US From: Fiona Ebner In-Reply-To: <20260225112851.124188-4-info@ebner-markus.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1772107468817 X-SPAM-LEVEL: Spam detection results: 0 AWL -1.075 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment RCVD_IN_VALIDITY_CERTIFIED_BLOCKED 0.618 ADMINISTRATOR NOTICE: The query to Validity was blocked. See https://knowledge.validity.com/hc/en-us/articles/20961730681243 for more information. RCVD_IN_VALIDITY_RPBL_BLOCKED 0.734 ADMINISTRATOR NOTICE: The query to Validity was blocked. See https://knowledge.validity.com/hc/en-us/articles/20961730681243 for more information. RCVD_IN_VALIDITY_SAFE_BLOCKED 0.78 ADMINISTRATOR NOTICE: The query to Validity was blocked. See https://knowledge.validity.com/hc/en-us/articles/20961730681243 for more information. SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Message-ID-Hash: NF5UD4CDLUGJEXJY3BLJOZ6XRSSTXTAQ X-Message-ID-Hash: NF5UD4CDLUGJEXJY3BLJOZ6XRSSTXTAQ X-MailFrom: f.ebner@proxmox.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list List-Id: Proxmox VE development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Am 25.02.26 um 1:06 PM schrieb Markus Ebner: > The previous implementation only allowed reads of fixed size starting > at byte offset 0. This made the Proxmox's agent/file-read unsuitable > for reading large files. > The new offset parameter allows specifying a byte offset position > relative to the start of the file (offset 0) from which the following > read should be performed. The implementation's behavior follows the > lseek semantics - directly following qemu-guest-agent's behavior: > > - fseek() does not perform validation against the file size > - Seeking beyond the end of the file is not an error but explicitly > allowed and specified behavior > - Subsequent fread() calls at positions beyond the file size return > zero bytes > > Additionally, this is equivalent to the behavior of POSIX pread(). > Reading a large file block-by-block thus becomes (pseudo-code): > let content = []; > while(response.truncated) { > response = proxmox.agent_file_read(offset = content.length); > content .= response.content; > } > > To be backwards compatible, offset defaults to 0. > > Signed-off-by: Markus Ebner Reviewed-by: Fiona Ebner