From: Willem de Bruijn Date: Tue, 25 Feb 2025 02:33:55 +0000 (-0500) Subject: net: skb: free up one bit in tx_flags X-Git-Tag: v6.15-rc1~160^2~216 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=e6116fc605574bb58c2016938ff24a7fbafe6e2a;p=thirdparty%2Fkernel%2Flinux.git net: skb: free up one bit in tx_flags The linked series wants to add skb tx completion timestamps. That needs a bit in skb_shared_info.tx_flags, but all are in use. A per-skb bit is only needed for features that are configured on a per packet basis. Per socket features can be read from sk->sk_tsflags. Per packet tsflags can be set in sendmsg using cmsg, but only those in SOF_TIMESTAMPING_TX_RECORD_MASK. Per packet tsflags can also be set without cmsg by sandwiching a send inbetween two setsockopts: val |= SOF_TIMESTAMPING_$FEATURE; setsockopt(fd, SOL_SOCKET, SO_TIMESTAMPING, &val, sizeof(val)); write(fd, buf, sz); val &= ~SOF_TIMESTAMPING_$FEATURE; setsockopt(fd, SOL_SOCKET, SO_TIMESTAMPING, &val, sizeof(val)); Changing a datapath test from skb_shinfo(skb)->tx_flags to skb->sk->sk_tsflags can change behavior in that case, as the tx_flags is written before the second setsockopt updates sk_tsflags. Therefore, only bits can be reclaimed that cannot be set by cmsg and are also highly unlikely to be used to target individual packets otherwise. Free up the bit currently used for SKBTX_HW_TSTAMP_USE_CYCLES. This selects between clock and free running counter source for HW TX timestamps. It is probable that all packets of the same socket will always use the same source. Link: https://lore.kernel.org/netdev/cover.1739988644.git.pav@iki.fi/ Signed-off-by: Willem de Bruijn Reviewed-by: Jason Xing Reviewed-by: Gerhard Engleder Link: https://patch.msgid.link/20250225023416.2088705-1-willemdebruijn.kernel@gmail.com Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/ethernet/engleder/tsnep_main.c b/drivers/net/ethernet/engleder/tsnep_main.c index 0d030cb0b21c7..3de4cb06e2668 100644 --- a/drivers/net/ethernet/engleder/tsnep_main.c +++ b/drivers/net/ethernet/engleder/tsnep_main.c @@ -852,8 +852,8 @@ static bool tsnep_tx_poll(struct tsnep_tx *tx, int napi_budget) struct skb_shared_hwtstamps hwtstamps; u64 timestamp; - if (skb_shinfo(entry->skb)->tx_flags & - SKBTX_HW_TSTAMP_USE_CYCLES) + if (entry->skb->sk && + READ_ONCE(entry->skb->sk->sk_tsflags) & SOF_TIMESTAMPING_BIND_PHC) timestamp = __le64_to_cpu(entry->desc_wb->counter); else diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c index 3044392e8ded8..472f009630c98 100644 --- a/drivers/net/ethernet/intel/igc/igc_main.c +++ b/drivers/net/ethernet/intel/igc/igc_main.c @@ -1668,7 +1668,8 @@ done: if (igc_request_tx_tstamp(adapter, skb, &tstamp_flags)) { skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS; tx_flags |= IGC_TX_FLAGS_TSTAMP | tstamp_flags; - if (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP_USE_CYCLES) + if (skb->sk && + READ_ONCE(skb->sk->sk_tsflags) & SOF_TIMESTAMPING_BIND_PHC) tx_flags |= IGC_TX_FLAGS_TSTAMP_TIMER_1; } else { adapter->tx_hwtstamp_skipped++; diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index f2bb8473d99a5..171aa15f65414 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -478,8 +478,8 @@ enum { /* device driver is going to provide hardware time stamp */ SKBTX_IN_PROGRESS = 1 << 2, - /* generate hardware time stamp based on cycles if supported */ - SKBTX_HW_TSTAMP_USE_CYCLES = 1 << 3, + /* reserved */ + SKBTX_RESERVED = 1 << 3, /* generate wifi status information (where possible) */ SKBTX_WIFI_STATUS = 1 << 4, @@ -500,7 +500,6 @@ enum { SKBTX_SCHED_TSTAMP | \ SKBTX_BPF) #define SKBTX_ANY_TSTAMP (SKBTX_HW_TSTAMP | \ - SKBTX_HW_TSTAMP_USE_CYCLES | \ SKBTX_ANY_SW_TSTAMP) /* Definitions for flags in struct skb_shared_info */ diff --git a/net/socket.c b/net/socket.c index 0545e9ea70581..b64ecf2722e7b 100644 --- a/net/socket.c +++ b/net/socket.c @@ -680,18 +680,9 @@ void __sock_tx_timestamp(__u32 tsflags, __u8 *tx_flags) { u8 flags = *tx_flags; - if (tsflags & SOF_TIMESTAMPING_TX_HARDWARE) { + if (tsflags & SOF_TIMESTAMPING_TX_HARDWARE) flags |= SKBTX_HW_TSTAMP_NOBPF; - /* PTP hardware clocks can provide a free running cycle counter - * as a time base for virtual clocks. Tell driver to use the - * free running cycle counter for timestamp if socket is bound - * to virtual clock. - */ - if (tsflags & SOF_TIMESTAMPING_BIND_PHC) - flags |= SKBTX_HW_TSTAMP_USE_CYCLES; - } - if (tsflags & SOF_TIMESTAMPING_TX_SOFTWARE) flags |= SKBTX_SW_TSTAMP;