From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by smtp.lore.kernel.org (Postfix) with ESMTP id 55F6FC54EFC for ; Fri, 20 Feb 2026 05:49:44 +0000 (UTC) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 32B3D406B4; Fri, 20 Feb 2026 06:48:52 +0100 (CET) Received: from mail-qv1-f45.google.com (mail-qv1-f45.google.com [209.85.219.45]) by mails.dpdk.org (Postfix) with ESMTP id 8283840678 for ; Fri, 20 Feb 2026 06:48:48 +0100 (CET) Received: by mail-qv1-f45.google.com with SMTP id 6a1803df08f44-896fa834290so19587236d6.1 for ; Thu, 19 Feb 2026 21:48:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20230601.gappssmtp.com; s=20230601; t=1771566528; x=1772171328; darn=dpdk.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=FX3nZFBP3EJDtIuZL8I+GEgURZS6cCmm2/u5sMmB3kE=; b=jONxfdViyu3zu3LCVB76Lum8ZYBvkqCdZlZLVPn1zCGxpm2K4bNjHwPNODPubx+VLv xbv2WfY6N4qKfamAjRvs8+xa53T2/kVlVvQ3BBhLJq1T+MCSYkiyqqAI7gyVnWx3tI9c OTS/cKpLCfJy/maFZNMbA25ErvioorvnkP9smDl510m8EmvYuTOnD0F/1kfe5LxtDscF rjsjIWDFQpwxGxqVhIA8oIePdx9nM+dyxL6Mnew+qHi72Rt5q4wHutU280wRgxqrAVk8 fYAA8M1soS/stc0gi/76dUQw2jA5jQJH5Vj5soA38Qyzh1//yiYjYZslAWbjkgA1i5WL hkTw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1771566528; x=1772171328; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to; bh=FX3nZFBP3EJDtIuZL8I+GEgURZS6cCmm2/u5sMmB3kE=; b=uPM+9TbNgDuddYCpCOkHqnxfSy7Aij2SjfXzsxzvRVS9E/avQ3noUN4nEWIFY5K0Dv nRBiaUqn/5UVvjmBdNlUmVH0t/xgtltIC9frCB/oQsB39W5LDByspxQKHiuhhCC5gSD1 2PEO/xMJ9AnHS7VPfFNHy3T+Wn3K2Y0s0DPz9ksDrpMzk29azfn6ApWuPwyak8vRtDzn lK+9la72n/eAhlYdZ0Y+lW05bsVmEyS83S41+TOizDqIohTcB3yPaIi0xQOlH8gPLCJn +962tvEbloKECMdkF6cb8KMj2qaAFm3eybA4moQfspZZj6N/xw/uZeE24a6/9haAAaKb tZvQ== X-Gm-Message-State: AOJu0Yz2hbGfW49qvxuqVJQ9O1OwIsNOsEZVqVbk/SzFdSyz5uzdlEe/ P8CnxCB5cmHCXk3QtcV0ZRCQybDbdf06pGHrBG5L+ZobcGbi3HvtL20j3R7xy+hL5QkgwQbE70M lM6Lt X-Gm-Gg: AZuq6aL+1zzu0LNe4GtwYdmSpRSIMyLUgOJCpIDxWOgykUHTKZppRnAxgKUCBEN22Mu uYdkfF1Cev3YYPCnSO5DPrbLjPUb1r6YxKCt2pKST2WN/XUamIAfrvQhm/GyqsyI+CBZNRPQE/d 5NcD3UgidFkTOM4Tbd57lP3HLsBPUEupyXd57g8fC6JaDDofJsWg8cqjnEbLkzY8wFQXmmhe6ul Xjr08oci4ss6TExGeFHkzu8cSLs+BxeeXwxj3Okg7YH22CZ90wfTZrc7wpSXV0dQiknIsTqIMrJ el0PEZTzWkd8GIvOG9y8ft9QgmuOBaTLEqEXciu4AerLQuWdjBhR3BuNL+lDuiT3hExmZfV2Bdu dPX8u40cB0Z7J5ppImemMZNkqEK3uzIZ9Q5EHy+KUiI5BQ23srt/xopACoVELqGvzwx+yX+Bd2v RGiFSxK50ZHJm2G3sLAPh703c9NUlRzM44yFAAOn6oF/KQns7XXb8fGdXjDvJD9g== X-Received: by 2002:ad4:5ded:0:b0:895:4aee:ac8d with SMTP id 6a1803df08f44-89965b45016mr57951956d6.21.1771566527804; Thu, 19 Feb 2026 21:48:47 -0800 (PST) Received: from phoenix.lan (204-195-96-226.wavecable.com. [204.195.96.226]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-8971cdad6c1sm229078096d6.39.2026.02.19.21.48.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Feb 2026 21:48:47 -0800 (PST) From: Stephen Hemminger To: dev@dpdk.org Cc: Stephen Hemminger , stable@dpdk.org, Ferruh Yigit , David Marchand Subject: [PATCH v17 09/23] net/pcap: fix error accounting and backpressure on transmit Date: Thu, 19 Feb 2026 21:45:44 -0800 Message-ID: <20260220054834.1632201-10-stephen@networkplumber.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260220054834.1632201-1-stephen@networkplumber.org> References: <20260106182823.192350-1-stephen@networkplumber.org> <20260220054834.1632201-1-stephen@networkplumber.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org The error handling when pcap_sendpacket() was incorrect. When underlying kernel socket buffer got full the send was counted as an error. Malformed multi-segment mbufs where pkt_len exceeds actual data were silently accepted. Malformed mbufs are now detected via rte_pktmbuf_read() failure and counted as errors. On Linux, pcap_sendpacket() calls send() on a blocking PF_PACKET socket with default kernel buffer sizes and no TX ring (PACKET_TX_RING). The send() call only blocks when the kernel socket send buffer is full, providing limited backpressure. Backpressure is not an error. Fixes: fbbbf553f268 ("net/pcap: fix concurrent multiseg Tx") Cc: stable@dpdk.org Signed-off-by: Stephen Hemminger --- drivers/net/pcap/pcap_ethdev.c | 77 +++++++++++++++++++++------------- 1 file changed, 49 insertions(+), 28 deletions(-) diff --git a/drivers/net/pcap/pcap_ethdev.c b/drivers/net/pcap/pcap_ethdev.c index 4cf5319839..1ab5b1755c 100644 --- a/drivers/net/pcap/pcap_ethdev.c +++ b/drivers/net/pcap/pcap_ethdev.c @@ -407,22 +407,27 @@ eth_pcap_tx_dumper(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) * dumper */ for (i = 0; i < nb_pkts; i++) { struct rte_mbuf *mbuf = bufs[i]; - size_t len, caplen; + uint32_t len, caplen; + const uint8_t *data; len = caplen = rte_pktmbuf_pkt_len(mbuf); calculate_timestamp(&header.ts); header.len = len; header.caplen = caplen; - /* rte_pktmbuf_read() returns a pointer to the data directly - * in the mbuf (when the mbuf is contiguous) or, otherwise, - * a pointer to temp_data after copying into it. - */ - pcap_dump((u_char *)dumper, &header, - rte_pktmbuf_read(mbuf, 0, caplen, temp_data)); - num_tx++; - tx_bytes += caplen; + data = rte_pktmbuf_read(mbuf, 0, caplen, temp_data); + if (unlikely(data == NULL)) { + /* This only happens if mbuf is bogus pkt_len > data_len */ + PMD_LOG(ERR, "rte_pktmbuf_read failed"); + dumper_q->tx_stat.err_pkts++; + } else { + pcap_dump((u_char *)dumper, &header, data); + + num_tx++; + tx_bytes += caplen; + } + rte_pktmbuf_free(mbuf); } @@ -434,9 +439,8 @@ eth_pcap_tx_dumper(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) pcap_dump_flush(dumper); dumper_q->tx_stat.pkts += num_tx; dumper_q->tx_stat.bytes += tx_bytes; - dumper_q->tx_stat.err_pkts += nb_pkts - num_tx; - return nb_pkts; + return i; } /* @@ -461,7 +465,17 @@ eth_tx_drop(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) } /* - * Callback to handle sending packets through a real NIC. + * Send a burst of packets to a pcap device. + * + * On Linux, pcap_sendpacket() calls send() on a blocking PF_PACKET + * socket with default kernel buffer sizes and no TX ring (PACKET_TX_RING). + * The send() call only blocks when the kernel socket send buffer is full, + * providing limited backpressure. + * + * On error, pcap_sendpacket() returns non-zero and the loop breaks, + * leaving remaining packets unsent. + * + * Bottom line: backpressure is not an error. */ static uint16_t eth_pcap_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) @@ -483,34 +497,41 @@ eth_pcap_tx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) for (i = 0; i < nb_pkts; i++) { struct rte_mbuf *mbuf = bufs[i]; - size_t len = rte_pktmbuf_pkt_len(mbuf); - int ret; + uint32_t len = rte_pktmbuf_pkt_len(mbuf); + const uint8_t *data; - if (unlikely(!rte_pktmbuf_is_contiguous(mbuf) && - len > RTE_ETH_PCAP_SNAPSHOT_LEN)) { + if (unlikely(!rte_pktmbuf_is_contiguous(mbuf) && len > RTE_ETH_PCAP_SNAPSHOT_LEN)) { PMD_LOG(ERR, - "Dropping multi segment PCAP packet. Size (%zd) > max size (%u).", + "Dropping multi segment PCAP packet. Size (%u) > max size (%u).", len, RTE_ETH_PCAP_SNAPSHOT_LEN); + tx_queue->tx_stat.err_pkts++; rte_pktmbuf_free(mbuf); continue; } - /* rte_pktmbuf_read() returns a pointer to the data directly - * in the mbuf (when the mbuf is contiguous) or, otherwise, - * a pointer to temp_data after copying into it. - */ - ret = pcap_sendpacket(pcap, - rte_pktmbuf_read(mbuf, 0, len, temp_data), len); - if (unlikely(ret != 0)) - break; - num_tx++; - tx_bytes += len; + data = rte_pktmbuf_read(mbuf, 0, len, temp_data); + if (unlikely(data == NULL)) { + /* This only happens if mbuf is bogus pkt_len > data_len */ + PMD_LOG(ERR, "rte_pktmbuf_read failed"); + tx_queue->tx_stat.err_pkts++; + } else { + /* + * No good way to separate back pressure from failure here + * Assume it is EBUSY, ENOMEM, or EINTR, something that can be retried. + */ + if (pcap_sendpacket(pcap, data, len) != 0) { + PMD_LOG(ERR, "pcap_sendpacket() failed: %s", pcap_geterr(pcap)); + break; + } + num_tx++; + tx_bytes += len; + } + rte_pktmbuf_free(mbuf); } tx_queue->tx_stat.pkts += num_tx; tx_queue->tx_stat.bytes += tx_bytes; - tx_queue->tx_stat.err_pkts += i - num_tx; return i; } -- 2.51.0