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 062C0FCC9AE for ; Tue, 10 Mar 2026 02:50:41 +0000 (UTC) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 1082640B9D; Tue, 10 Mar 2026 03:49:43 +0100 (CET) Received: from mail-ot1-f49.google.com (mail-ot1-f49.google.com [209.85.210.49]) by mails.dpdk.org (Postfix) with ESMTP id 13C8440A6E for ; Tue, 10 Mar 2026 03:49:39 +0100 (CET) Received: by mail-ot1-f49.google.com with SMTP id 46e09a7af769-7d738fe814cso2658253a34.3 for ; Mon, 09 Mar 2026 19:49:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20230601.gappssmtp.com; s=20230601; t=1773110978; x=1773715778; 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=Zm1lLo6/5f3siTudzDSeyzelNMDWiISK8xbrptcURpsH0VsN7vxMbHNJ+s43tDwW3z fOa3JxkrRcKjbn/fsLTctWrszB7zNGYdBZGC1pBdvZ5SpStbzoOIKbansE6Y4dgacY+c y0NEEGk0k6hMWulSVV9+o4KNQOzjmP1YWUrw8wYcnGTy6DMzhIyskhkkiVPoVjEq28MN iv2MXe+il29/j7OFe+DyoURnb6sUg51ezcvhIdSHqgc0aGSaWQILxQVwvJunZzS2Ehv4 jM6jr/XIORZAuIL4ZPTET1wl/CsZXD/gX17DSaYzYL5WY1ikyRV6P01rXpi/ARgjK95v ayEQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1773110978; x=1773715778; 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=m8ltX77OFPH/+tvr5Tgjpvxa5CV2d3C3uF35QZE0Ctli5yzZafbFjjMdI+wL14aXiD vnO5hO8Zw9bkGvZ/7gOWD5wMuRSj6dydbtCQHRsW2HSwVNV7X+WFxpZjXQuqY9iWtgu7 i1a7M1WURxAXY8mfggWoaDFasNGpuC1Xx88dSBBEAlhzhWk8beWzE1FzDlvggr4lRZSu ge5iG624sxG3hB28ze4Q3aNVMwwuvRPaTYV14kQ6Qqcigq6RXXdOTRwyajoGDtr04lqV cvAfqDpc/b06OmsxxotP/sjFcFY6EhRFioWERtcSk/HlhJF8QKh9AaYXdzWs2TdGbXiQ py9A== X-Gm-Message-State: AOJu0YwwvmekuhBCbRO0duzu2XtTdAcgxnCUFlIdx++4EXQ1Kezo+RuE LvS3Tm5H3/PPuDjOyWGJjZCGcxeTD0jR8RnzlSHDxz5oDX5eeDTy4DlZVV8H9qiZTTXvJfcKj53 M6w7KBg4= X-Gm-Gg: ATEYQzzs1LuaTV7nLPlIHeJH+cuYyQN8AvgIcampC4sB6fTBERUp1KjxZb7spaP8G7B 2ND9teUHavyNeSXVl/C3ANGjvKwVrSbJi72lbiqSI3I2va06+D1Zk8TRyOhq0C93Rgwphz47o3z OlJp2PjZl+O+qXoaFPuNKvKMTRD3ep8/11vAmNxcVRf4DHEQ51fZWE46On7gzZvavghJancUZp9 UeR4EzoZkeRuNp27YcSN17nszma4RZnCQPRgp6dWzSSsLjssaYiYXTcLPCNEBgGHrZiRWzCeI2r EBnigeKyKoLFTQZ0rPPpxrN5I9+z6tRBhWaSiiR0CqD25a9BB6zV7kIX2b4v9gpHPc8ISj6Txv/ RBZxPhq8cRpnP97csE7yy3bIMIYIFvt6qoXVDIvkvIAFWYFhDDJ8bo/zNJoRpq7LeAlQW9+BprK 6D1VWJQNte8vecPI5H3yRuJ++XrmWOLUxk X-Received: by 2002:a05:6830:6683:b0:7d7:45b7:ed93 with SMTP id 46e09a7af769-7d745b7eeb4mr4979776a34.15.1773110978348; Mon, 09 Mar 2026 19:49:38 -0700 (PDT) Received: from phoenix.lan ([104.202.29.139]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-7d728d1238csm7808572a34.15.2026.03.09.19.49.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Mar 2026 19:49:38 -0700 (PDT) From: Stephen Hemminger To: dev@dpdk.org Cc: Stephen Hemminger , stable@dpdk.org, David Marchand , Ferruh Yigit Subject: [PATCH v19 09/25] net/pcap: fix error accounting and backpressure on transmit Date: Mon, 9 Mar 2026 19:47:44 -0700 Message-ID: <20260310024925.476543-10-stephen@networkplumber.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260310024925.476543-1-stephen@networkplumber.org> References: <20260106182823.192350-1-stephen@networkplumber.org> <20260310024925.476543-1-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