Re: [dpdk-stable] patch 'gso: fix mbuf freeing responsibility' has been queued to stable release 19.11.6

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

Hi Luca,


> Hi,
> 
> FYI, your patch has been queued to stable release 19.11.6
> 
> Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
> It will be pushed if I get no objections before 11/11/20. So please
> shout if anyone has objections.

Not sure it has to be backported to 19.11 LTS.
Yes it fixes a problem, but it also introduces a functional change.
AFAIK, we have to avoid it with LTS patches.
Konstantin


> 
> Also note that after the patch there's a diff of the upstream commit vs the
> patch applied to the branch. This will indicate if there was any rebasing
> needed to apply to the stable branch. If there were code changes for rebasing
> (ie: not only metadata diffs), please double check that the rebase was
> correctly done.
> 
> Queued patches are on a temporary branch at:
> https://github.com/bluca/dpdk-stable
> 
> This queued commit can be viewed at:
> https://github.com/bluca/dpdk-stable/commit/6dce2ff12e8191ffd4d23e1ab9322f2d042f6e5b
> 
> Thanks.
> 
> Luca Boccassi
> 
> ---
> From 6dce2ff12e8191ffd4d23e1ab9322f2d042f6e5b Mon Sep 17 00:00:00 2001
> From: Yi Yang <yangyi01@inspur.com>
> Date: Mon, 26 Oct 2020 14:47:13 +0800
> Subject: [PATCH] gso: fix mbuf freeing responsibility
> 
> [ upstream commit c0d002aed98d6d1d38d6bb318a5bd2ed5cdc01b1 ]
> 
> rte_gso_segment decreased refcnt of pkt by one, but
> it is wrong if pkt is external mbuf, pkt won't be
> freed because of incorrect refcnt, the result is
> application can't allocate mbuf from mempool because
> mbufs in mempool are run out of.
> 
> One correct way is application should call
> rte_pktmbuf_free after calling rte_gso_segment to free
> pkt explicitly. rte_gso_segment must not handle it, this
> should be responsibility of application.
> 
> This commit changed rte_gso_segment in functional behavior
> and return value, so the application must take appropriate
> actions according to return values, "ret < 0" means it
> should free and drop 'pkt', "ret == 0" means 'pkt' isn't
> GSOed but 'pkt' can be transmitted as a normal packet,
> "ret > 0" means 'pkt' has been GSOed into two or multiple
> segments, it should use "pkts_out" to transmit these
> segments. The application must free 'pkt' after call
> rte_gso_segment when return value isn't equal to 0.
> 
> Fixes: 119583797b6a ("gso: support TCP/IPv4 GSO")
> 
> Signed-off-by: Yi Yang <yangyi01@inspur.com>
> Acked-by: Jiayu Hu <jiayu.hu@intel.com>
> Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> ---
>  app/test-pmd/csumonly.c                           | 12 ++++++++++--
>  .../generic_segmentation_offload_lib.rst          |  7 +++++--
>  drivers/net/tap/rte_eth_tap.c                     | 12 ++++++++++--
>  lib/librte_gso/gso_tcp4.c                         |  6 ++----
>  lib/librte_gso/gso_tunnel_tcp4.c                  | 14 +++++---------
>  lib/librte_gso/gso_udp4.c                         |  6 ++----
>  lib/librte_gso/rte_gso.c                          | 15 +++------------
>  lib/librte_gso/rte_gso.h                          |  8 ++++++--
>  8 files changed, 43 insertions(+), 37 deletions(-)
> 
> diff --git a/app/test-pmd/csumonly.c b/app/test-pmd/csumonly.c
> index 7b92ab1195..d0eef8b51c 100644
> --- a/app/test-pmd/csumonly.c
> +++ b/app/test-pmd/csumonly.c
> @@ -1050,9 +1050,17 @@ tunnel_update:
>  			ret = rte_gso_segment(pkts_burst[i], gso_ctx,
>  					&gso_segments[nb_segments],
>  					GSO_MAX_PKT_BURST - nb_segments);
> -			if (ret >= 0)
> +			if (ret >= 1) {
> +				/* pkts_burst[i] can be freed safely here. */
> +				rte_pktmbuf_free(pkts_burst[i]);
>  				nb_segments += ret;
> -			else {
> +			} else if (ret == 0) {
> +				/* 0 means it can be transmitted directly
> +				 * without gso.
> +				 */
> +				gso_segments[nb_segments] = pkts_burst[i];
> +				nb_segments += 1;
> +			} else {
>  				TESTPMD_LOG(DEBUG, "Unable to segment packet");
>  				rte_pktmbuf_free(pkts_burst[i]);
>  			}
> diff --git a/doc/guides/prog_guide/generic_segmentation_offload_lib.rst b/doc/guides/prog_guide/generic_segmentation_offload_lib.rst
> index 205cb8a866..ad91c6e5fc 100644
> --- a/doc/guides/prog_guide/generic_segmentation_offload_lib.rst
> +++ b/doc/guides/prog_guide/generic_segmentation_offload_lib.rst
> @@ -25,8 +25,9 @@ Bearing that in mind, the GSO library enables DPDK applications to segment
>  packets in software. Note however, that GSO is implemented as a standalone
>  library, and not via a 'fallback' mechanism (i.e. for when TSO is unsupported
>  in the underlying hardware); that is, applications must explicitly invoke the
> -GSO library to segment packets. The size of GSO segments ``(segsz)`` is
> -configurable by the application.
> +GSO library to segment packets, they also must call ``rte_pktmbuf_free()``
> +to free mbuf GSO segments attached after calling ``rte_gso_segment()``.
> +The size of GSO segments (``segsz``) is configurable by the application.
> 
>  Limitations
>  -----------
> @@ -233,6 +234,8 @@ To segment an outgoing packet, an application must:
> 
>  #. Invoke the GSO segmentation API, ``rte_gso_segment()``.
> 
> +#. Call ``rte_pktmbuf_free()`` to free mbuf ``rte_gso_segment()`` segments.
> +
>  #. If required, update the L3 and L4 checksums of the newly-created segments.
>     For tunneled packets, the outer IPv4 headers' checksums should also be
>     updated. Alternatively, the application may offload checksum calculation
> diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
> index cfbd579cd6..1e2f21d96f 100644
> --- a/drivers/net/tap/rte_eth_tap.c
> +++ b/drivers/net/tap/rte_eth_tap.c
> @@ -713,8 +713,16 @@ pmd_tx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>  			if (num_tso_mbufs < 0)
>  				break;
> 
> -			mbuf = gso_mbufs;
> -			num_mbufs = num_tso_mbufs;
> +			if (num_tso_mbufs >= 1) {
> +				mbuf = gso_mbufs;
> +				num_mbufs = num_tso_mbufs;
> +			} else {
> +				/* 0 means it can be transmitted directly
> +				 * without gso.
> +				 */
> +				mbuf = &mbuf_in;
> +				num_mbufs = 1;
> +			}
>  		} else {
>  			/* stats.errs will be incremented */
>  			if (rte_pktmbuf_pkt_len(mbuf_in) > max_size)
> diff --git a/lib/librte_gso/gso_tcp4.c b/lib/librte_gso/gso_tcp4.c
> index ade172ac73..d31feaff95 100644
> --- a/lib/librte_gso/gso_tcp4.c
> +++ b/lib/librte_gso/gso_tcp4.c
> @@ -50,15 +50,13 @@ gso_tcp4_segment(struct rte_mbuf *pkt,
>  			pkt->l2_len);
>  	frag_off = rte_be_to_cpu_16(ipv4_hdr->fragment_offset);
>  	if (unlikely(IS_FRAGMENTED(frag_off))) {
> -		pkts_out[0] = pkt;
> -		return 1;
> +		return 0;
>  	}
> 
>  	/* Don't process the packet without data */
>  	hdr_offset = pkt->l2_len + pkt->l3_len + pkt->l4_len;
>  	if (unlikely(hdr_offset >= pkt->pkt_len)) {
> -		pkts_out[0] = pkt;
> -		return 1;
> +		return 0;
>  	}
> 
>  	pyld_unit_size = gso_size - hdr_offset;
> diff --git a/lib/librte_gso/gso_tunnel_tcp4.c b/lib/librte_gso/gso_tunnel_tcp4.c
> index e0384c26d0..166aace73a 100644
> --- a/lib/librte_gso/gso_tunnel_tcp4.c
> +++ b/lib/librte_gso/gso_tunnel_tcp4.c
> @@ -62,7 +62,7 @@ gso_tunnel_tcp4_segment(struct rte_mbuf *pkt,
>  {
>  	struct rte_ipv4_hdr *inner_ipv4_hdr;
>  	uint16_t pyld_unit_size, hdr_offset, frag_off;
> -	int ret = 1;
> +	int ret;
> 
>  	hdr_offset = pkt->outer_l2_len + pkt->outer_l3_len + pkt->l2_len;
>  	inner_ipv4_hdr = (struct rte_ipv4_hdr *)(rte_pktmbuf_mtod(pkt, char *) +
> @@ -73,25 +73,21 @@ gso_tunnel_tcp4_segment(struct rte_mbuf *pkt,
>  	 */
>  	frag_off = rte_be_to_cpu_16(inner_ipv4_hdr->fragment_offset);
>  	if (unlikely(IS_FRAGMENTED(frag_off))) {
> -		pkts_out[0] = pkt;
> -		return 1;
> +		return 0;
>  	}
> 
>  	hdr_offset += pkt->l3_len + pkt->l4_len;
>  	/* Don't process the packet without data */
>  	if (hdr_offset >= pkt->pkt_len) {
> -		pkts_out[0] = pkt;
> -		return 1;
> +		return 0;
>  	}
>  	pyld_unit_size = gso_size - hdr_offset;
> 
>  	/* Segment the payload */
>  	ret = gso_do_segment(pkt, hdr_offset, pyld_unit_size, direct_pool,
>  			indirect_pool, pkts_out, nb_pkts_out);
> -	if (ret <= 1)
> -		return ret;
> -
> -	update_tunnel_ipv4_tcp_headers(pkt, ipid_delta, pkts_out, ret);
> +	if (ret > 1)
> +		update_tunnel_ipv4_tcp_headers(pkt, ipid_delta, pkts_out, ret);
> 
>  	return ret;
>  }
> diff --git a/lib/librte_gso/gso_udp4.c b/lib/librte_gso/gso_udp4.c
> index 6fa68f243a..5d0186aa24 100644
> --- a/lib/librte_gso/gso_udp4.c
> +++ b/lib/librte_gso/gso_udp4.c
> @@ -52,8 +52,7 @@ gso_udp4_segment(struct rte_mbuf *pkt,
>  			pkt->l2_len);
>  	frag_off = rte_be_to_cpu_16(ipv4_hdr->fragment_offset);
>  	if (unlikely(IS_FRAGMENTED(frag_off))) {
> -		pkts_out[0] = pkt;
> -		return 1;
> +		return 0;
>  	}
> 
>  	/*
> @@ -65,8 +64,7 @@ gso_udp4_segment(struct rte_mbuf *pkt,
> 
>  	/* Don't process the packet without data. */
>  	if (unlikely(hdr_offset + pkt->l4_len >= pkt->pkt_len)) {
> -		pkts_out[0] = pkt;
> -		return 1;
> +		return 0;
>  	}
> 
>  	/* pyld_unit_size must be a multiple of 8 because frag_off
> diff --git a/lib/librte_gso/rte_gso.c b/lib/librte_gso/rte_gso.c
> index 751b5b625e..896350ebc8 100644
> --- a/lib/librte_gso/rte_gso.c
> +++ b/lib/librte_gso/rte_gso.c
> @@ -30,7 +30,6 @@ rte_gso_segment(struct rte_mbuf *pkt,
>  		uint16_t nb_pkts_out)
>  {
>  	struct rte_mempool *direct_pool, *indirect_pool;
> -	struct rte_mbuf *pkt_seg;
>  	uint64_t ol_flags;
>  	uint16_t gso_size;
>  	uint8_t ipid_delta;
> @@ -44,8 +43,7 @@ rte_gso_segment(struct rte_mbuf *pkt,
> 
>  	if (gso_ctx->gso_size >= pkt->pkt_len) {
>  		pkt->ol_flags &= (~(PKT_TX_TCP_SEG | PKT_TX_UDP_SEG));
> -		pkts_out[0] = pkt;
> -		return 1;
> +		return 0;
>  	}
> 
>  	direct_pool = gso_ctx->direct_pool;
> @@ -75,18 +73,11 @@ rte_gso_segment(struct rte_mbuf *pkt,
>  				indirect_pool, pkts_out, nb_pkts_out);
>  	} else {
>  		/* unsupported packet, skip */
> -		pkts_out[0] = pkt;
>  		RTE_LOG(DEBUG, GSO, "Unsupported packet type\n");
> -		return 1;
> +		ret = 0;
>  	}
> 
> -	if (ret > 1) {
> -		pkt_seg = pkt;
> -		while (pkt_seg) {
> -			rte_mbuf_refcnt_update(pkt_seg, -1);
> -			pkt_seg = pkt_seg->next;
> -		}
> -	} else if (ret < 0) {
> +	if (ret < 0) {
>  		/* Revert the ol_flags in the event of failure. */
>  		pkt->ol_flags = ol_flags;
>  	}
> diff --git a/lib/librte_gso/rte_gso.h b/lib/librte_gso/rte_gso.h
> index 3aab297f44..d93ee8e5b1 100644
> --- a/lib/librte_gso/rte_gso.h
> +++ b/lib/librte_gso/rte_gso.h
> @@ -89,8 +89,11 @@ struct rte_gso_ctx {
>   * the GSO segments are sent to should support transmission of multi-segment
>   * packets.
>   *
> - * If the input packet is GSO'd, its mbuf refcnt reduces by 1. Therefore,
> - * when all GSO segments are freed, the input packet is freed automatically.
> + * If the input packet is GSO'd, all the indirect segments are attached to the
> + * input packet.
> + *
> + * rte_gso_segment() will not free the input packet no matter whether it is
> + * GSO'd or not, the application should free it after calling rte_gso_segment().
>   *
>   * If the memory space in pkts_out or MBUF pools is insufficient, this
>   * function fails, and it returns (-1) * errno. Otherwise, GSO succeeds,
> @@ -109,6 +112,7 @@ struct rte_gso_ctx {
>   *
>   * @return
>   *  - The number of GSO segments filled in pkts_out on success.
> + *  - Return 0 if it does not need to be GSO'd.
>   *  - Return -ENOMEM if run out of memory in MBUF pools.
>   *  - Return -EINVAL for invalid parameters.
>   */
> --
> 2.27.0
> 
> ---
>   Diff of the applied patch vs upstream commit (please double-check if non-empty:
> ---
> --- -	2020-11-09 18:40:12.168193728 +0000
> +++ 0024-gso-fix-mbuf-freeing-responsibility.patch	2020-11-09 18:40:11.103310846 +0000
> @@ -1 +1 @@
> -From c0d002aed98d6d1d38d6bb318a5bd2ed5cdc01b1 Mon Sep 17 00:00:00 2001
> +From 6dce2ff12e8191ffd4d23e1ab9322f2d042f6e5b Mon Sep 17 00:00:00 2001
> @@ -5,0 +6,2 @@
> +[ upstream commit c0d002aed98d6d1d38d6bb318a5bd2ed5cdc01b1 ]
> +
> @@ -28 +29,0 @@
> -Cc: stable@dpdk.org
> @@ -36 +36,0 @@
> - doc/guides/rel_notes/release_20_11.rst            |  6 ++++++
> @@ -43 +43 @@
> - 9 files changed, 49 insertions(+), 37 deletions(-)
> + 8 files changed, 43 insertions(+), 37 deletions(-)
> @@ -46 +46 @@
> -index 3d7d244d1e..d813d4fae0 100644
> +index 7b92ab1195..d0eef8b51c 100644
> @@ -49 +49 @@
> -@@ -1080,9 +1080,17 @@ tunnel_update:
> +@@ -1050,9 +1050,17 @@ tunnel_update:
> @@ -94,17 +93,0 @@
> -diff --git a/doc/guides/rel_notes/release_20_11.rst b/doc/guides/rel_notes/release_20_11.rst
> -index 7c8246d1b3..1524f61915 100644
> ---- a/doc/guides/rel_notes/release_20_11.rst
> -+++ b/doc/guides/rel_notes/release_20_11.rst
> -@@ -569,6 +569,12 @@ API Changes
> -
> - * bpf: ``RTE_BPF_XTYPE_NUM`` has been dropped from ``rte_bpf_xtype``.
> -
> -+* gso: Changed ``rte_gso_segment`` behaviour and return value:
> -+
> -+  * ``pkt`` is not saved to ``pkts_out[0]`` if not GSOed.
> -+  * Return 0 instead of 1 for the above case.
> -+  * ``pkt`` is not freed, no matter whether it is GSOed, leaving to the caller.
> -+
> - * acl: ``RTE_ACL_CLASSIFY_NUM`` enum value has been removed.
> -   This enum value was not used inside DPDK, while it prevented to add new
> -   classify algorithms without causing an ABI breakage.
> @@ -112 +95 @@
> -index 81c688471d..2f8abb12c5 100644
> +index cfbd579cd6..1e2f21d96f 100644
> @@ -115 +98 @@
> -@@ -751,8 +751,16 @@ pmd_tx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
> +@@ -713,8 +713,16 @@ pmd_tx_burst(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)