| Message ID | 20220302195519.3479274-1-kafai@fb.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | Preserve mono delivery time (EDT) in skb->tstamp | expand |
On Wed, Mar 2, 2022 at 11:55 AM Martin KaFai Lau <kafai@fb.com> wrote: > > skb->tstamp was first used as the (rcv) timestamp. > The major usage is to report it to the user (e.g. SO_TIMESTAMP). > > Later, skb->tstamp is also set as the (future) delivery_time (e.g. EDT in TCP) > during egress and used by the qdisc (e.g. sch_fq) to make decision on when > the skb can be passed to the dev. > > Currently, there is no way to tell skb->tstamp having the (rcv) timestamp > or the delivery_time, so it is always reset to 0 whenever forwarded > between egress and ingress. > > While it makes sense to always clear the (rcv) timestamp in skb->tstamp > to avoid confusing sch_fq that expects the delivery_time, it is a > performance issue [0] to clear the delivery_time if the skb finally > egress to a fq@phy-dev. > > This set is to keep the mono delivery time and make it available to > the final egress interface. Please see individual patch for > the details. > > [0] (slide 22): https://linuxplumbersconf.org/event/11/contributions/953/attachments/867/1658/LPC_2021_BPF_Datapath_Extensions.pdf > For the whole series Reviewed-by: Eric Dumazet <edumazet@google.com> Thanks !
Hello: This series was applied to netdev/net-next.git (master) by David S. Miller <davem@davemloft.net>: On Wed, 2 Mar 2022 11:55:19 -0800 you wrote: > skb->tstamp was first used as the (rcv) timestamp. > The major usage is to report it to the user (e.g. SO_TIMESTAMP). > > Later, skb->tstamp is also set as the (future) delivery_time (e.g. EDT in TCP) > during egress and used by the qdisc (e.g. sch_fq) to make decision on when > the skb can be passed to the dev. > > [...] Here is the summary with links: - [v6,net-next,01/13] net: Add skb->mono_delivery_time to distinguish mono delivery_time from (rcv) timestamp https://git.kernel.org/netdev/net-next/c/a1ac9c8acec1 - [v6,net-next,02/13] net: Add skb_clear_tstamp() to keep the mono delivery_time https://git.kernel.org/netdev/net-next/c/de799101519a - [v6,net-next,03/13] net: Handle delivery_time in skb->tstamp during network tapping with af_packet https://git.kernel.org/netdev/net-next/c/27942a15209f - [v6,net-next,04/13] net: Clear mono_delivery_time bit in __skb_tstamp_tx() https://git.kernel.org/netdev/net-next/c/d93376f503c7 - [v6,net-next,05/13] net: Set skb->mono_delivery_time and clear it after sch_handle_ingress() https://git.kernel.org/netdev/net-next/c/d98d58a00261 - [v6,net-next,06/13] net: ip: Handle delivery_time in ip defrag https://git.kernel.org/netdev/net-next/c/8672406eb5d7 - [v6,net-next,07/13] net: ipv6: Handle delivery_time in ipv6 defrag https://git.kernel.org/netdev/net-next/c/335c8cf3b537 - [v6,net-next,08/13] net: ipv6: Get rcv timestamp if needed when handling hop-by-hop IOAM option https://git.kernel.org/netdev/net-next/c/b6561f8491ca - [v6,net-next,09/13] net: Get rcv tstamp if needed in nfnetlink_{log, queue}.c https://git.kernel.org/netdev/net-next/c/80fcec675112 - [v6,net-next,10/13] net: Postpone skb_clear_delivery_time() until knowing the skb is delivered locally https://git.kernel.org/netdev/net-next/c/cd14e9b7b8d3 - [v6,net-next,11/13] bpf: Keep the (rcv) timestamp behavior for the existing tc-bpf@ingress https://git.kernel.org/netdev/net-next/c/7449197d600d - [v6,net-next,12/13] bpf: Add __sk_buff->delivery_time_type and bpf_skb_set_skb_delivery_time() https://git.kernel.org/netdev/net-next/c/8d21ec0e46ed - [v6,net-next,13/13] bpf: selftests: test skb->tstamp in redirect_neigh https://git.kernel.org/netdev/net-next/c/c803475fd8dd You are awesome, thank you!
skb->tstamp was first used as the (rcv) timestamp. The major usage is to report it to the user (e.g. SO_TIMESTAMP). Later, skb->tstamp is also set as the (future) delivery_time (e.g. EDT in TCP) during egress and used by the qdisc (e.g. sch_fq) to make decision on when the skb can be passed to the dev. Currently, there is no way to tell skb->tstamp having the (rcv) timestamp or the delivery_time, so it is always reset to 0 whenever forwarded between egress and ingress. While it makes sense to always clear the (rcv) timestamp in skb->tstamp to avoid confusing sch_fq that expects the delivery_time, it is a performance issue [0] to clear the delivery_time if the skb finally egress to a fq@phy-dev. This set is to keep the mono delivery time and make it available to the final egress interface. Please see individual patch for the details. [0] (slide 22): https://linuxplumbersconf.org/event/11/contributions/953/attachments/867/1658/LPC_2021_BPF_Datapath_Extensions.pdf v6: - Add kdoc and use non-UAPI type in patch 6 (Jakub) v5: netdev: - Patch 3 in v4 is broken down into smaller patches 3, 4, and 5 in v5 - The mono_delivery_time bit clearing in __skb_tstamp_tx() is done in __net_timestamp() instead. This is patch 4 in v5. - Missed a skb_clear_delivery_time() for the 'skip_classify' case in dev.c in v4. That is fixed in patch 5 in v5 for correctness. The skb_clear_delivery_time() will be moved to a later stage in Patch 10, so it was an intermediate error in v4. - Added delivery time handling for nfnetlink_{log, queue}.c in patch 9 (Daniel) - Added delivery time handling in the IPv6 IOAM hop-by-hop option which has an experimental IANA assigned value 49 in patch 8 - Added delivery time handling in nf_conntrack for the ipv6 defrag case in patch 7 - Removed unlikely() from testing skb->mono_delivery_time (Daniel) bpf: - Remove the skb->tstamp dance in ingress. Depends on bpf insn rewrite to return 0 if skb->tstamp has delivery time in patch 11. It is to backward compatible with the existing tc-bpf@ingress in patch 11. - bpf_set_delivery_time() will also allow dtime == 0 and dtime_type == BPF_SKB_DELIVERY_TIME_NONE as argument in patch 12. v4: netdev: - Push the skb_clear_delivery_time() from ip_local_deliver() and ip6_input() to ip_local_deliver_finish() and ip6_input_finish() to accommodate the ipvs forward path. This is the notable change in v4 at the netdev side. - Patch 3/8 first does the skb_clear_delivery_time() after sch_handle_ingress() in dev.c and this will make the tc-bpf forward path work via the bpf_redirect_*() helper. - The next patch 4/8 (new in v4) will then postpone the skb_clear_delivery_time() from dev.c to the ip_local_deliver_finish() and ip6_input_finish() after taking care of the tstamp usage in the ip defrag case. This will make the kernel forward path also work, e.g. the ip[6]_forward(). - Fixed a case v3 which missed setting the skb->mono_delivery_time bit when sending TCP rst/ack in some cases (e.g. from a ctl_sk). That case happens at ip_send_unicast_reply() and tcp_v6_send_response(). It is fixed in patch 1/8 (and then patch 3/8) in v4. bpf: - Adding __sk_buff->delivery_time_type instead of adding __sk_buff->mono_delivery_time as in v3. The tc-bpf can stay with one __sk_buff->tstamp instead of having two 'time' fields while one is 0 and another is not. tc-bpf can use the new __sk_buff->delivery_time_type to tell what is stored in __sk_buff->tstamp. - bpf_skb_set_delivery_time() helper is added to set __sk_buff->tstamp from non mono delivery_time to mono delivery_time - Most of the convert_ctx_access() bpf insn rewrite in v3 is gone, so no new rewrite added for __sk_buff->tstamp. The only rewrite added is for reading the new __sk_buff->delivery_time_type. - Added selftests, test_tc_dtime.c v3: - Feedback from v2 is using shinfo(skb)->tx_flags could be racy. - Considered to reuse a few bits in skb->tstamp to represent different semantics, other than more code churns, it will break the bpf usecase which currently can write and then read back the skb->tstamp. - Went back to v1 idea on adding a bit to skb and address the feedbacks on v1: - Added one bit skb->mono_delivery_time to flag that the skb->tstamp has the mono delivery_time (EDT), instead of adding a bit to flag if the skb->tstamp has been forwarded or not. - Instead of resetting the delivery_time back to the (rcv) timestamp during recvmsg syscall which may be too late and not useful, the delivery_time reset in v3 happens earlier once the stack knows that the skb will be delivered locally. - Handled the tapping@ingress case by af_packet - No need to change the (rcv) timestamp to mono clock base as in v1. The added one bit to flag skb->mono_delivery_time is enough to keep the EDT delivery_time during forward. - Added logic to the bpf side to make the existing bpf running at ingress can still get the (rcv) timestamp when reading the __sk_buff->tstamp. New __sk_buff->mono_delivery_time is also added. Test is still needed to test this piece. Martin KaFai Lau (13): net: Add skb->mono_delivery_time to distinguish mono delivery_time from (rcv) timestamp net: Add skb_clear_tstamp() to keep the mono delivery_time net: Handle delivery_time in skb->tstamp during network tapping with af_packet net: Clear mono_delivery_time bit in __skb_tstamp_tx() net: Set skb->mono_delivery_time and clear it after sch_handle_ingress() net: ip: Handle delivery_time in ip defrag net: ipv6: Handle delivery_time in ipv6 defrag net: ipv6: Get rcv timestamp if needed when handling hop-by-hop IOAM option net: Get rcv tstamp if needed in nfnetlink_{log, queue}.c net: Postpone skb_clear_delivery_time() until knowing the skb is delivered locally bpf: Keep the (rcv) timestamp behavior for the existing tc-bpf@ingress bpf: Add __sk_buff->delivery_time_type and bpf_skb_set_skb_delivery_time() bpf: selftests: test skb->tstamp in redirect_neigh drivers/net/loopback.c | 2 +- include/linux/filter.h | 3 +- include/linux/skbuff.h | 74 ++- include/net/inet_frag.h | 2 + include/uapi/linux/bpf.h | 41 +- net/bridge/br_forward.c | 2 +- net/bridge/netfilter/nf_conntrack_bridge.c | 5 +- net/core/dev.c | 8 +- net/core/filter.c | 178 ++++++- net/core/skbuff.c | 4 +- net/ieee802154/6lowpan/reassembly.c | 1 + net/ipv4/inet_fragment.c | 1 + net/ipv4/ip_forward.c | 2 +- net/ipv4/ip_fragment.c | 1 + net/ipv4/ip_input.c | 1 + net/ipv4/ip_output.c | 6 +- net/ipv4/tcp_output.c | 16 +- net/ipv6/ioam6.c | 19 +- net/ipv6/ip6_input.c | 1 + net/ipv6/ip6_output.c | 7 +- net/ipv6/netfilter.c | 5 +- net/ipv6/netfilter/nf_conntrack_reasm.c | 1 + net/ipv6/reassembly.c | 1 + net/ipv6/tcp_ipv6.c | 2 +- net/netfilter/ipvs/ip_vs_xmit.c | 6 +- net/netfilter/nf_dup_netdev.c | 2 +- net/netfilter/nf_flow_table_ip.c | 4 +- net/netfilter/nfnetlink_log.c | 6 +- net/netfilter/nfnetlink_queue.c | 8 +- net/netfilter/nft_fwd_netdev.c | 2 +- net/openvswitch/vport.c | 2 +- net/packet/af_packet.c | 4 +- net/sched/act_bpf.c | 2 + net/sched/cls_bpf.c | 2 + net/xfrm/xfrm_interface.c | 2 +- tools/include/uapi/linux/bpf.h | 41 +- .../selftests/bpf/prog_tests/tc_redirect.c | 434 ++++++++++++++++++ .../selftests/bpf/progs/test_tc_dtime.c | 349 ++++++++++++++ 38 files changed, 1174 insertions(+), 73 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/test_tc_dtime.c