Hi Jiayu, Thanks for the comments. I have replied inline below. Will address the review comments, but I think this would be a good patch to have in general. Please let me know your thoughts. On Tue, Jun 20, 2023 at 1:06 PM Hu, Jiayu wrote: > Hi Kumara, > > Please see replies inline. > > Thanks, > Jiayu > > > -----Original Message----- > > From: Kumara Parameshwaran > > Sent: Tuesday, November 1, 2022 3:06 PM > > To: Hu, Jiayu > > Cc: dev@dpdk.org; Kumara Parameshwaran > > ; Kumara Parameshwaran > > > > Subject: [PATCH v5] gro : fix reordering of packets in GRO library > > > > From: Kumara Parameshwaran > > > > When a TCP packet contains flags like PSH it is returned immediately to > the > > application though there might be packets of the same flow in the GRO > table. > > If PSH flag is set on a segment packets up to the segment should be > delivered > > immediately. But the current implementation delivers the last arrived > packet > > with PSH flag set causing re-ordering > > > > With this patch, if a packet does not contain only ACK flag and if there > are no > > previous packets for the flow the packet would be returned immediately, > > else will be merged with the previous segment and the flag on the last > > segment will be set on the entire segment. > > This is the behaviour with linux stack as well. > > > > Signed-off-by: Kumara Parameshwaran > > Co-authored-by: Kumara Parameshwaran > > --- > > v1: > > If the received packet is not a pure ACK packet, we check if > > there are any previous packets in the flow, if present we indulge > > the received packet also in the coalescing logic and update the > flags > > of the last recived packet to the entire segment which would avoid > > re-ordering. > > > > Lets say a case where P1(PSH), P2(ACK), P3(ACK) are received in > > burst mode, > > P1 contains PSH flag and since it does not contain any prior > packets in > > the flow > > we copy it to unprocess_packets and P2(ACK) and P3(ACK) are > > merged together. > > In the existing case the P2,P3 would be delivered as single > segment > > first and the > > unprocess_packets will be copied later which will cause reordering. > > With the patch > > copy the unprocess packets first and then the packets from the GRO > > table. > > > > Testing done > > The csum test-pmd was modifited to support the following > > GET request of 10MB from client to server via test-pmd (static arp > > entries added in client > > and server). Enable GRO and TSO in test-pmd where the packets > > recived from the client mac > > would be sent to server mac and vice versa. > > In above testing, without the patch the client observerd > re-ordering > > of 25 packets > > and with the patch there were no packet re-ordering observerd. > > > > v2: > > Fix warnings in commit and comment. > > Do not consider packet as candidate to merge if it contains SYN/RST > > flag. > > > > v3: > > Fix warnings. > > > > v4: > > Rebase with master. > > > > v5: > > Adding co-author email > > > > lib/gro/gro_tcp4.c | 45 +++++++++++++++++++++++++++++++++++++-------- > > lib/gro/rte_gro.c | 18 +++++++++--------- > > 2 files changed, 46 insertions(+), 17 deletions(-) > > > > diff --git a/lib/gro/gro_tcp4.c b/lib/gro/gro_tcp4.c index > > 0014096e63..7363c5d540 100644 > > --- a/lib/gro/gro_tcp4.c > > +++ b/lib/gro/gro_tcp4.c > > @@ -188,6 +188,19 @@ update_header(struct gro_tcp4_item *item) > > pkt->l2_len); > > } > > > > +static inline void > > +update_tcp_hdr_flags(struct rte_tcp_hdr *tcp_hdr, struct rte_mbuf *pkt) > > +{ > > + struct rte_ether_hdr *eth_hdr; > > + struct rte_ipv4_hdr *ipv4_hdr; > > + struct rte_tcp_hdr *merged_tcp_hdr; > > + > > + eth_hdr = rte_pktmbuf_mtod(pkt, struct rte_ether_hdr *); > > + ipv4_hdr = (struct rte_ipv4_hdr *)((char *)eth_hdr + pkt->l2_len); > > + merged_tcp_hdr = (struct rte_tcp_hdr *)((char *)ipv4_hdr + pkt- > > >l3_len); > > + merged_tcp_hdr->tcp_flags |= tcp_hdr->tcp_flags; } > > The Linux kernel updates the TCP flag via "tcp_flag_word(th2) |= flags & > (TCP_FLAG_FIN | TCP_FLAG_PSH)", > which only adds FIN and PSH at most to the merge packet. > >> Sure, will change it to add only FIN and PSH. >> > > > + > > int32_t > > gro_tcp4_reassemble(struct rte_mbuf *pkt, > > struct gro_tcp4_tbl *tbl, > > @@ -206,6 +219,7 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt, > > uint32_t i, max_flow_num, remaining_flow_num; > > int cmp; > > uint8_t find; > > + uint32_t start_idx; > > > > /* > > * Don't process the packet whose TCP header length is greater @@ - > > 219,13 +233,6 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt, > > tcp_hdr = (struct rte_tcp_hdr *)((char *)ipv4_hdr + pkt->l3_len); > > hdr_len = pkt->l2_len + pkt->l3_len + pkt->l4_len; > > > > - /* > > - * Don't process the packet which has FIN, SYN, RST, PSH, URG, ECE > > - * or CWR set. > > - */ > > - if (tcp_hdr->tcp_flags != RTE_TCP_ACK_FLAG) > > - return -1; > > - > > /* trim the tail padding bytes */ > > ip_tlen = rte_be_to_cpu_16(ipv4_hdr->total_length); > > if (pkt->pkt_len > (uint32_t)(ip_tlen + pkt->l2_len)) @@ -264,12 > > +271,30 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt, > > if (tbl->flows[i].start_index != INVALID_ARRAY_INDEX) { > > if (is_same_tcp4_flow(tbl->flows[i].key, key)) { > > find = 1; > > + start_idx = tbl->flows[i].start_index; > > break; > > } > > remaining_flow_num--; > > } > > } > > > > + if (tcp_hdr->tcp_flags != RTE_TCP_ACK_FLAG) { > > + /* > > + * Check and try merging the current TCP segment with the > > previous > > + * TCP segment if the TCP header does not contain RST and > > SYN flag > > + * There are cases where the last segment is sent with > > FIN|PSH|ACK > > + * which should also be considered for merging with > previous > > segments. > > + */ > > + if (find && !(tcp_hdr->tcp_flags & > > (RTE_TCP_RST_FLAG|RTE_TCP_SYN_FLAG))) > > + /* > > + * Since PSH flag is set, start time will be set > to 0 so it > > will be flushed > > + * immediately. > > + */ > > + tbl->items[start_idx].start_time = 0; > > + else > > + return -1; > > + } > > The nested if-else check is not straightforward, and it's hard to read the > condition-action of > different combinations of flag bits. In addition, are all flag bits > considered like Linux kernel? > >> Not all bits are considered. Will fix to make sure that all bits are >> considered. Will try to reorganise the code better. Let me know if you have >> any other suggestions here. >> > > > + > > /* > > * Fail to find a matched flow. Insert a new flow and store the > > * packet into the flow. > > @@ -304,8 +329,12 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt, > > is_atomic); > > if (cmp) { > > if (merge_two_tcp4_packets(&(tbl->items[cur_idx]), > > - pkt, cmp, sent_seq, ip_id, > 0)) > > + pkt, cmp, sent_seq, ip_id, > 0)) > > { > > + if (tbl->items[cur_idx].start_time == 0) > > + update_tcp_hdr_flags(tcp_hdr, tbl- > > >items[cur_idx].firstseg); > > return 1; > > + } > > + > > /* > > * Fail to merge the two packets, as the packet > > * length is greater than the max value. Store > diff --git > > a/lib/gro/rte_gro.c b/lib/gro/rte_gro.c index e35399fd42..87c5502dce > > 100644 > > --- a/lib/gro/rte_gro.c > > +++ b/lib/gro/rte_gro.c > > @@ -283,10 +283,17 @@ rte_gro_reassemble_burst(struct rte_mbuf **pkts, > > if ((nb_after_gro < nb_pkts) > > || (unprocess_num < nb_pkts)) { > > i = 0; > > + /* Copy unprocessed packets */ > > + if (unprocess_num > 0) { > > + memcpy(&pkts[i], unprocess_pkts, > > + sizeof(struct rte_mbuf *) * > > + unprocess_num); > > + i = unprocess_num; > > + } > > Why copy unprocess pkts first? This is for avoiding out-of-order? > > Thanks, > Jiayu > > /* Flush all packets from the tables */ > > if (do_vxlan_tcp_gro) { > > - i = > gro_vxlan_tcp4_tbl_timeout_flush(&vxlan_tcp_tbl, > > - 0, pkts, nb_pkts); > > + i += > > gro_vxlan_tcp4_tbl_timeout_flush(&vxlan_tcp_tbl, > > + 0, &pkts[i], nb_pkts - i); > > } > > > > if (do_vxlan_udp_gro) { > > @@ -304,13 +311,6 @@ rte_gro_reassemble_burst(struct rte_mbuf **pkts, > > i += gro_udp4_tbl_timeout_flush(&udp_tbl, 0, > > &pkts[i], nb_pkts - i); > > } > > - /* Copy unprocessed packets */ > > - if (unprocess_num > 0) { > > - memcpy(&pkts[i], unprocess_pkts, > > - sizeof(struct rte_mbuf *) * > > - unprocess_num); > > - } > > - nb_after_gro = i + unprocess_num; > > } > > > > return nb_after_gro; > > -- > > 2.25.1 > >