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 6639AFD4F05 for ; Tue, 10 Mar 2026 16:15:24 +0000 (UTC) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 5B97640E4B; Tue, 10 Mar 2026 17:14:14 +0100 (CET) Received: from mail-ot1-f48.google.com (mail-ot1-f48.google.com [209.85.210.48]) by mails.dpdk.org (Postfix) with ESMTP id 5E0C940E36 for ; Tue, 10 Mar 2026 17:14:11 +0100 (CET) Received: by mail-ot1-f48.google.com with SMTP id 46e09a7af769-7d73d6976adso2237292a34.2 for ; Tue, 10 Mar 2026 09:14:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20230601.gappssmtp.com; s=20230601; t=1773159250; x=1773764050; 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=8BWz+1HDX4Te0zgjn4oPVTzDBFfvbeL/ycSMs259YBM=; b=rLmbn7ZKIVt7HSUHxzSkVGkxqokODvm31TmaSkl2aDYoFFuqEZWWcSpnhvsWIRDbsd I+trLdcoYzORrVw7uBl3SrpaShjtezEb/1EsW9Mt4m85pEOuJYSyvFzrgf7V67fknPuz GizxKRmLYgmqHZebDbzAOmkiAfQA+dNc6oZyWf16gArSL3jbiBwNQR4Jz4RubxO96mVZ sOlo2xyAY50XV9MfL/NkLXhISvbAjpyBegjsEUmpky9E9C6WFhKDpqWV4DkvaD83a4m2 HDCBQ7M3PThfTdUWfxpBfAZiEIHB0l681MGmrCrzM7E4cqdKbJVFoYC9mf91PxzpVYLu wsTg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1773159250; x=1773764050; 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=8BWz+1HDX4Te0zgjn4oPVTzDBFfvbeL/ycSMs259YBM=; b=TiN+4V2Rnl/gFoJoFAPC//utCnOdOJYm/O9DwLrMiTQf4h/jlgTThmZegBGT0YvA9o 8evDO24wxwOu3OxCOlDIMInZOs93gPDk/3MzGF1Z9kg4TPtZXTAuZivNDO100wZHnx+u Cs1YE9rPDppn8K8qbDM3pGX0g5e0J+vATQkDHA/SuoPl/lKmOG/Q+P/DFKTnko0n4BK9 UH2AXw4dZl39qJTmTdya6JRSNxLqz8JywtRZkiN6XOmhqRZuxGvz5alprMVYq+jN7NDg 0F+abxp5KtfgTi6gOM4nxSqHrAm6f66JPHTpuTdXwNsBz3HvEaoFlX7qfCqKCbPdAPT3 9LYA== X-Gm-Message-State: AOJu0YzSS9IghtLNU5eAEZzSrfUOo1EyCv9RZHQM3mbe6mLePXciAeAU KNHyQoR3rRwUm+4d7fA1vSwr3NUrngZKf7XUtH09ZJbohdYoQjNxJiu2OJ9OR+T/ENxSn1XSVOq u+h8XVT8= X-Gm-Gg: ATEYQzxRFF1VtVOKLisHJcybEMIUG3VJDfajQz7kHeqIgEQ7m+1V/p7FyLrryr8TVQN 53KdeJ8Rq+W2UYJSyVuirEnzzK4nDRmJL+dhhT9k9+N/I4fCehIrQrJZyDtxtioAcwPpcXVWijU IUFu+k6bwzp0pmq1qHIWvjCzKMNMRVIUZ1rzBq9arc+2+aCT4ExjxAVqysjykfc48Ea/MnpaCaf jdDQ8VNmwrsKBAKKsbWsvPI/zBqeA6mrg0Euy6O1q1GPHWiVpzAyntyB4JejM4jyoATkqTQeFLV Bn3r9uvjW1gtpLzt4PmHoPMuxD3SPb/NK7jAcynExIYxbyfoAHDxvaPIOwC7hSyXBlFH8q4ji4I 96LVtTHWf0TNV9nkOa4g8A40AErE6ywPkfhhi4vfT2hHLvGwdAJKhLJ3BBOKvNIbBndyNgrXMZA MpZ3nW+gtUEnWvL+xbIh5b1fMZKssRMm6a X-Received: by 2002:a9d:630d:0:b0:7d7:4009:1ad with SMTP id 46e09a7af769-7d740090acemr4431394a34.2.1773159250667; Tue, 10 Mar 2026 09:14:10 -0700 (PDT) Received: from phoenix.lan ([104.202.29.139]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7d738e3f421sm7304004a34.25.2026.03.10.09.14.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Mar 2026 09:14:10 -0700 (PDT) From: Stephen Hemminger To: dev@dpdk.org Cc: Stephen Hemminger , stable@dpdk.org, David Marchand , Ferruh Yigit Subject: [PATCH v20 09/25] net/pcap: fix error accounting and backpressure on transmit Date: Tue, 10 Mar 2026 09:09:47 -0700 Message-ID: <20260310161356.194553-10-stephen@networkplumber.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260310161356.194553-1-stephen@networkplumber.org> References: <20260106182823.192350-1-stephen@networkplumber.org> <20260310161356.194553-1-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. 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 | 58 +++++++++++++++++++++------------- 1 file changed, 36 insertions(+), 22 deletions(-) diff --git a/drivers/net/pcap/pcap_ethdev.c b/drivers/net/pcap/pcap_ethdev.c index 72a297d423..47a050df11 100644 --- a/drivers/net/pcap/pcap_ethdev.c +++ b/drivers/net/pcap/pcap_ethdev.c @@ -407,7 +407,8 @@ 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 = rte_pktmbuf_pkt_len(mbuf); caplen = RTE_MIN(len, RTE_ETH_PCAP_SNAPSHOT_LEN); @@ -415,15 +416,16 @@ eth_pcap_tx_dumper(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts) 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)); + + data = rte_pktmbuf_read(mbuf, 0, caplen, temp_data); + + /* This could only happen if mbuf is bogus pkt_len > data_len */ + RTE_ASSERT(data != NULL); + pcap_dump((u_char *)dumper, &header, data); num_tx++; tx_bytes += caplen; + rte_pktmbuf_free(mbuf); } @@ -435,9 +437,8 @@ 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; } /* @@ -462,7 +463,17 @@ 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) @@ -484,34 +495,37 @@ 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. + data = rte_pktmbuf_read(mbuf, 0, len, temp_data); + RTE_ASSERT(data != NULL); + + /* + * No good way to separate back pressure from failure here + * Assume it is EBUSY, ENOMEM, or EINTR, something that can be retried. */ - ret = pcap_sendpacket(pcap, - rte_pktmbuf_read(mbuf, 0, len, temp_data), len); - if (unlikely(ret != 0)) + 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