| Message ID | ce8cc5ce6e25d5e455704aa42fbf633be206ce85.1701334869.git.lorenzo@kernel.org (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | add multi-buff support for xdp running in generic mode | expand |
On 11/30/23 10:11, Lorenzo Bianconi wrote: > Similar to native xdp, do not always linearize the skb in > netif_receive_generic_xdp routine but create a non-linear xdp_buff to be > processed by the eBPF program. This allow to add multi-buffer support > for xdp running in generic mode. > > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org> > --- > net/core/dev.c | 144 ++++++++++++++++++++++++++++++++++++++++--------- > 1 file changed, 119 insertions(+), 25 deletions(-) > > diff --git a/net/core/dev.c b/net/core/dev.c > index 4df68d7f04a2..0d08e755bb7f 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -4853,6 +4853,12 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > xdp_init_buff(xdp, frame_sz, &rxqueue->xdp_rxq); > xdp_prepare_buff(xdp, hard_start, skb_headroom(skb) - mac_len, > skb_headlen(skb) + mac_len, true); > + if (skb_is_nonlinear(skb)) { > + skb_shinfo(skb)->xdp_frags_size = skb->data_len; > + xdp_buff_set_frags_flag(xdp); > + } else { > + xdp_buff_clear_frags_flag(xdp); > + } > > orig_data_end = xdp->data_end; > orig_data = xdp->data; > @@ -4882,6 +4888,14 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > skb->len += off; /* positive on grow, negative on shrink */ > } > > + /* XDP frag metadata (e.g. nr_frags) are updated in eBPF helpers > + * (e.g. bpf_xdp_adjust_tail), we need to update data_len here. > + */ > + if (xdp_buff_has_frags(xdp)) > + skb->data_len = skb_shinfo(skb)->xdp_frags_size; > + else > + skb->data_len = 0; > + > /* check if XDP changed eth hdr such SKB needs update */ > eth = (struct ethhdr *)xdp->data; > if ((orig_eth_type != eth->h_proto) || > @@ -4915,54 +4929,134 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > return act; > } > > -static u32 netif_receive_generic_xdp(struct sk_buff **pskb, > - struct xdp_buff *xdp, > - struct bpf_prog *xdp_prog) > +static int netif_skb_check_for_generic_xdp(struct sk_buff **pskb, > + struct bpf_prog *prog) I like this is split out into a check function. > { > struct sk_buff *skb = *pskb; > - u32 act = XDP_DROP; > - > - /* Reinjected packets coming from act_mirred or similar should > - * not get XDP generic processing. > - */ > - if (skb_is_redirected(skb)) > - return XDP_PASS; (For other reviewers) This reinjected check is moved further down. > + int err; > > - /* XDP packets must be linear and must have sufficient headroom > - * of XDP_PACKET_HEADROOM bytes. This is the guarantee that also > - * native XDP provides, thus we need to do it here as well. > + /* XDP does not support fraglist so we need to linearize > + * the skb. > */ > - if (skb_cloned(skb) || skb_is_nonlinear(skb) || > - skb_headroom(skb) < XDP_PACKET_HEADROOM) { > + if (skb_has_frag_list(skb) || !prog->aux->xdp_has_frags) { > int hroom = XDP_PACKET_HEADROOM - skb_headroom(skb); > int troom = skb->tail + skb->data_len - skb->end; > > /* In case we have to go down the path and also linearize, > * then lets do the pskb_expand_head() work just once here. > */ > - if (pskb_expand_head(skb, > - hroom > 0 ? ALIGN(hroom, NET_SKB_PAD) : 0, > - troom > 0 ? troom + 128 : 0, GFP_ATOMIC)) > - goto do_drop; > - if (skb_linearize(skb)) > - goto do_drop; > + err = pskb_expand_head(skb, > + hroom > 0 ? ALIGN(hroom, NET_SKB_PAD) : 0, > + troom > 0 ? troom + 128 : 0, GFP_ATOMIC); > + if (err) > + return err; > + > + err = skb_linearize(skb); > + if (err) > + return err; > + > + return 0; > + } > + > + /* XDP packets must have sufficient headroom of XDP_PACKET_HEADROOM > + * bytes. This is the guarantee that also native XDP provides, > + * thus we need to do it here as well. > + */ > + if (skb_cloned(skb) || skb_shinfo(skb)->nr_frags || I though we could allow a SKB with skb_shinfo(skb)->nr_frags (that isn't cloned or shared) to be processed by generic XDP without any reallocation? So check would be: (skb_cloned(skb) || skb_shared(skb) ||) > + skb_headroom(skb) < XDP_PACKET_HEADROOM) { [Headroom trick] For layered devices the netstack could be the process that created the SKB. If you noticed my veth patchset[4/4], when I detect an XDP-prog attach, I'm increasing the net_device headroom (.ndo_set_rx_headroom) such that netstack will allocated enough headroom to satisfy XDP_PACKET_HEADROOM. [4/4] https://lore.kernel.org/netdev/169272716651.1975370.10514711233878278884.stgit@firesoul/ > + u32 mac_len = skb->data - skb_mac_header(skb); > + u32 size, len, max_head_size, off; > + struct sk_buff *nskb; > + int i, head_off; > + > + __skb_push(skb, mac_len); > + max_head_size = SKB_WITH_OVERHEAD(PAGE_SIZE - > + XDP_PACKET_HEADROOM); > + if (skb->len > max_head_size + MAX_SKB_FRAGS * PAGE_SIZE) > + return -ENOMEM; > + > + size = min_t(u32, skb->len, max_head_size); > + nskb = netdev_alloc_skb(skb->dev, size + XDP_PACKET_HEADROOM); Would is be possible to use napi_alloc_skb() here? The napi_alloc_skb() is faster than netdev_alloc_skb(), but it as name suggest assumes this is called under NAPI protection/context. It used-to-be the case for generic XDP, but code got moved around to support layered devices, so I not 100% sure if this is always true (NAPI context). > + if (!nskb) > + return -ENOMEM; > + > + skb_reserve(nskb, XDP_PACKET_HEADROOM); > + skb_copy_header(nskb, skb); > + > + err = skb_copy_bits(skb, 0, nskb->data, size); > + if (err) { > + consume_skb(nskb); > + return err; > + } > + skb_put(nskb, size); > + > + head_off = skb_headroom(nskb) - skb_headroom(skb); > + skb_headers_offset_update(nskb, head_off); > + > + off = size; > + len = skb->len - off; > + for (i = 0; i < MAX_SKB_FRAGS && off < skb->len; i++) { > + struct page *page; > + void *frag; > + > + size = min_t(u32, len, PAGE_SIZE); > + frag = netdev_alloc_frag(size); Again the slower variant. > + if (!frag) { > + consume_skb(nskb); > + return -ENOMEM; > + } > + > + page = virt_to_head_page(frag); > + skb_add_rx_frag(nskb, i, page, > + frag - page_address(page), size, size); > + err = skb_copy_bits(skb, off, frag, size); > + if (err) { > + consume_skb(nskb); > + return err; > + } > + > + len -= size; > + off += size; > + } > + > + consume_skb(skb); > + *pskb = nskb; > + __skb_pull(nskb, mac_len); > } > > - act = bpf_prog_run_generic_xdp(skb, xdp, xdp_prog); > + return 0; > +} > + > +static u32 netif_receive_generic_xdp(struct sk_buff **pskb, > + struct xdp_buff *xdp, > + struct bpf_prog *xdp_prog) > +{ > + u32 act = XDP_DROP; > + > + /* Reinjected packets coming from act_mirred or similar should > + * not get XDP generic processing. > + */ > + if (skb_is_redirected(*pskb)) > + return XDP_PASS; > + > + if (netif_skb_check_for_generic_xdp(pskb, xdp_prog)) > + goto do_drop; > + > + act = bpf_prog_run_generic_xdp(*pskb, xdp, xdp_prog); > switch (act) { > case XDP_REDIRECT: > case XDP_TX: > case XDP_PASS: > break; > default: > - bpf_warn_invalid_xdp_action(skb->dev, xdp_prog, act); > + bpf_warn_invalid_xdp_action((*pskb)->dev, xdp_prog, act); > fallthrough; > case XDP_ABORTED: > - trace_xdp_exception(skb->dev, xdp_prog, act); > + trace_xdp_exception((*pskb)->dev, xdp_prog, act); > fallthrough; > case XDP_DROP: > do_drop: > - kfree_skb(skb); > + kfree_skb(*pskb); > break; > } > Overall I like the patch :-) Are we missing more things to allow GRO packets getting processed by generic XDP? --Jesper
> > > On 11/30/23 10:11, Lorenzo Bianconi wrote: > > Similar to native xdp, do not always linearize the skb in > > netif_receive_generic_xdp routine but create a non-linear xdp_buff to be > > processed by the eBPF program. This allow to add multi-buffer support > > for xdp running in generic mode. > > > > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org> > > --- > > net/core/dev.c | 144 ++++++++++++++++++++++++++++++++++++++++--------- > > 1 file changed, 119 insertions(+), 25 deletions(-) > > > > diff --git a/net/core/dev.c b/net/core/dev.c > > index 4df68d7f04a2..0d08e755bb7f 100644 > > --- a/net/core/dev.c > > +++ b/net/core/dev.c > > @@ -4853,6 +4853,12 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > > xdp_init_buff(xdp, frame_sz, &rxqueue->xdp_rxq); > > xdp_prepare_buff(xdp, hard_start, skb_headroom(skb) - mac_len, > > skb_headlen(skb) + mac_len, true); > > + if (skb_is_nonlinear(skb)) { > > + skb_shinfo(skb)->xdp_frags_size = skb->data_len; > > + xdp_buff_set_frags_flag(xdp); > > + } else { > > + xdp_buff_clear_frags_flag(xdp); > > + } > > orig_data_end = xdp->data_end; > > orig_data = xdp->data; > > @@ -4882,6 +4888,14 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > > skb->len += off; /* positive on grow, negative on shrink */ > > } > > + /* XDP frag metadata (e.g. nr_frags) are updated in eBPF helpers > > + * (e.g. bpf_xdp_adjust_tail), we need to update data_len here. > > + */ > > + if (xdp_buff_has_frags(xdp)) > > + skb->data_len = skb_shinfo(skb)->xdp_frags_size; > > + else > > + skb->data_len = 0; > > + > > /* check if XDP changed eth hdr such SKB needs update */ > > eth = (struct ethhdr *)xdp->data; > > if ((orig_eth_type != eth->h_proto) || > > @@ -4915,54 +4929,134 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > > return act; > > } > > -static u32 netif_receive_generic_xdp(struct sk_buff **pskb, > > - struct xdp_buff *xdp, > > - struct bpf_prog *xdp_prog) > > +static int netif_skb_check_for_generic_xdp(struct sk_buff **pskb, > > + struct bpf_prog *prog) > > I like this is split out into a check function. > > > { > > struct sk_buff *skb = *pskb; > > - u32 act = XDP_DROP; > > - > > - /* Reinjected packets coming from act_mirred or similar should > > - * not get XDP generic processing. > > - */ > > - if (skb_is_redirected(skb)) > > - return XDP_PASS; > > (For other reviewers) > This reinjected check is moved further down. > > > + int err; > > - /* XDP packets must be linear and must have sufficient headroom > > - * of XDP_PACKET_HEADROOM bytes. This is the guarantee that also > > - * native XDP provides, thus we need to do it here as well. > > + /* XDP does not support fraglist so we need to linearize > > + * the skb. > > */ > > - if (skb_cloned(skb) || skb_is_nonlinear(skb) || > > - skb_headroom(skb) < XDP_PACKET_HEADROOM) { > > + if (skb_has_frag_list(skb) || !prog->aux->xdp_has_frags) { > > int hroom = XDP_PACKET_HEADROOM - skb_headroom(skb); > > int troom = skb->tail + skb->data_len - skb->end; > > /* In case we have to go down the path and also linearize, > > * then lets do the pskb_expand_head() work just once here. > > */ > > - if (pskb_expand_head(skb, > > - hroom > 0 ? ALIGN(hroom, NET_SKB_PAD) : 0, > > - troom > 0 ? troom + 128 : 0, GFP_ATOMIC)) > > - goto do_drop; > > - if (skb_linearize(skb)) > > - goto do_drop; > > + err = pskb_expand_head(skb, > > + hroom > 0 ? ALIGN(hroom, NET_SKB_PAD) : 0, > > + troom > 0 ? troom + 128 : 0, GFP_ATOMIC); > > + if (err) > > + return err; > > + > > + err = skb_linearize(skb); > > + if (err) > > + return err; > > + > > + return 0; > > + } > > + > > + /* XDP packets must have sufficient headroom of XDP_PACKET_HEADROOM > > + * bytes. This is the guarantee that also native XDP provides, > > + * thus we need to do it here as well. > > + */ > > + if (skb_cloned(skb) || skb_shinfo(skb)->nr_frags || > > I though we could allow a SKB with skb_shinfo(skb)->nr_frags (that isn't > cloned or shared) to be processed by generic XDP without any reallocation? I do not think so, we discussed about it with Jakub here [0] [0] https://lore.kernel.org/netdev/20231128105145.7b39db7d@kernel.org/ > > So check would be: (skb_cloned(skb) || skb_shared(skb) ||) > > > + skb_headroom(skb) < XDP_PACKET_HEADROOM) { > > [Headroom trick] > For layered devices the netstack could be the process that created the > SKB. If you noticed my veth patchset[4/4], when I detect an XDP-prog > attach, I'm increasing the net_device headroom (.ndo_set_rx_headroom) > such that netstack will allocated enough headroom to satisfy > XDP_PACKET_HEADROOM. > > [4/4] https://lore.kernel.org/netdev/169272716651.1975370.10514711233878278884.stgit@firesoul/ Ah nice, for some reason I missed this patch > > > > > + u32 mac_len = skb->data - skb_mac_header(skb); > > + u32 size, len, max_head_size, off; > > + struct sk_buff *nskb; > > + int i, head_off; > > + > > + __skb_push(skb, mac_len); > > + max_head_size = SKB_WITH_OVERHEAD(PAGE_SIZE - > > + XDP_PACKET_HEADROOM); > > + if (skb->len > max_head_size + MAX_SKB_FRAGS * PAGE_SIZE) > > + return -ENOMEM; > > + > > + size = min_t(u32, skb->len, max_head_size); > > + nskb = netdev_alloc_skb(skb->dev, size + XDP_PACKET_HEADROOM); > > > Would is be possible to use napi_alloc_skb() here? > > The napi_alloc_skb() is faster than netdev_alloc_skb(), but it as name > suggest assumes this is called under NAPI protection/context. It > used-to-be the case for generic XDP, but code got moved around to > support layered devices, so I not 100% sure if this is always true (NAPI > context). Actually I was thinking about it and I was not 100% sure too (so I decided to use the non-NAPI version). Any input about it? Regards, Lorenzo > > > > + if (!nskb) > > + return -ENOMEM; > > + > > + skb_reserve(nskb, XDP_PACKET_HEADROOM); > > + skb_copy_header(nskb, skb); > > + > > + err = skb_copy_bits(skb, 0, nskb->data, size); > > + if (err) { > > + consume_skb(nskb); > > + return err; > > + } > > + skb_put(nskb, size); > > + > > + head_off = skb_headroom(nskb) - skb_headroom(skb); > > + skb_headers_offset_update(nskb, head_off); > > + > > + off = size; > > + len = skb->len - off; > > + for (i = 0; i < MAX_SKB_FRAGS && off < skb->len; i++) { > > + struct page *page; > > + void *frag; > > + > > + size = min_t(u32, len, PAGE_SIZE); > > + frag = netdev_alloc_frag(size); > > Again the slower variant. > > > + if (!frag) { > > + consume_skb(nskb); > > + return -ENOMEM; > > + } > > + > > + page = virt_to_head_page(frag); > > + skb_add_rx_frag(nskb, i, page, > > + frag - page_address(page), size, size); > > + err = skb_copy_bits(skb, off, frag, size); > > + if (err) { > > + consume_skb(nskb); > > + return err; > > + } > > + > > + len -= size; > > + off += size; > > + } > > + > > + consume_skb(skb); > > + *pskb = nskb; > > + __skb_pull(nskb, mac_len); > > } > > - act = bpf_prog_run_generic_xdp(skb, xdp, xdp_prog); > > + return 0; > > +} > > + > > +static u32 netif_receive_generic_xdp(struct sk_buff **pskb, > > + struct xdp_buff *xdp, > > + struct bpf_prog *xdp_prog) > > +{ > > + u32 act = XDP_DROP; > > + > > + /* Reinjected packets coming from act_mirred or similar should > > + * not get XDP generic processing. > > + */ > > + if (skb_is_redirected(*pskb)) > > + return XDP_PASS; > > + > > + if (netif_skb_check_for_generic_xdp(pskb, xdp_prog)) > > + goto do_drop; > > + > > + act = bpf_prog_run_generic_xdp(*pskb, xdp, xdp_prog); > > switch (act) { > > case XDP_REDIRECT: > > case XDP_TX: > > case XDP_PASS: > > break; > > default: > > - bpf_warn_invalid_xdp_action(skb->dev, xdp_prog, act); > > + bpf_warn_invalid_xdp_action((*pskb)->dev, xdp_prog, act); > > fallthrough; > > case XDP_ABORTED: > > - trace_xdp_exception(skb->dev, xdp_prog, act); > > + trace_xdp_exception((*pskb)->dev, xdp_prog, act); > > fallthrough; > > case XDP_DROP: > > do_drop: > > - kfree_skb(skb); > > + kfree_skb(*pskb); > > break; > > } > > Overall I like the patch :-) > > Are we missing more things to allow GRO packets getting processed by generic > XDP? > > --Jesper
On 11/30, Lorenzo Bianconi wrote: > > > > > > On 11/30/23 10:11, Lorenzo Bianconi wrote: > > > Similar to native xdp, do not always linearize the skb in > > > netif_receive_generic_xdp routine but create a non-linear xdp_buff to be > > > processed by the eBPF program. This allow to add multi-buffer support > > > for xdp running in generic mode. > > > > > > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org> > > > --- > > > net/core/dev.c | 144 ++++++++++++++++++++++++++++++++++++++++--------- > > > 1 file changed, 119 insertions(+), 25 deletions(-) > > > > > > diff --git a/net/core/dev.c b/net/core/dev.c > > > index 4df68d7f04a2..0d08e755bb7f 100644 > > > --- a/net/core/dev.c > > > +++ b/net/core/dev.c > > > @@ -4853,6 +4853,12 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > > > xdp_init_buff(xdp, frame_sz, &rxqueue->xdp_rxq); > > > xdp_prepare_buff(xdp, hard_start, skb_headroom(skb) - mac_len, > > > skb_headlen(skb) + mac_len, true); > > > + if (skb_is_nonlinear(skb)) { > > > + skb_shinfo(skb)->xdp_frags_size = skb->data_len; > > > + xdp_buff_set_frags_flag(xdp); > > > + } else { > > > + xdp_buff_clear_frags_flag(xdp); > > > + } > > > orig_data_end = xdp->data_end; > > > orig_data = xdp->data; > > > @@ -4882,6 +4888,14 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > > > skb->len += off; /* positive on grow, negative on shrink */ > > > } > > > + /* XDP frag metadata (e.g. nr_frags) are updated in eBPF helpers > > > + * (e.g. bpf_xdp_adjust_tail), we need to update data_len here. > > > + */ > > > + if (xdp_buff_has_frags(xdp)) > > > + skb->data_len = skb_shinfo(skb)->xdp_frags_size; > > > + else > > > + skb->data_len = 0; > > > + > > > /* check if XDP changed eth hdr such SKB needs update */ > > > eth = (struct ethhdr *)xdp->data; > > > if ((orig_eth_type != eth->h_proto) || > > > @@ -4915,54 +4929,134 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > > > return act; > > > } > > > -static u32 netif_receive_generic_xdp(struct sk_buff **pskb, > > > - struct xdp_buff *xdp, > > > - struct bpf_prog *xdp_prog) > > > +static int netif_skb_check_for_generic_xdp(struct sk_buff **pskb, > > > + struct bpf_prog *prog) > > > > I like this is split out into a check function. > > > > > { > > > struct sk_buff *skb = *pskb; > > > - u32 act = XDP_DROP; > > > - > > > - /* Reinjected packets coming from act_mirred or similar should > > > - * not get XDP generic processing. > > > - */ > > > - if (skb_is_redirected(skb)) > > > - return XDP_PASS; > > > > (For other reviewers) > > This reinjected check is moved further down. > > > > > + int err; > > > - /* XDP packets must be linear and must have sufficient headroom > > > - * of XDP_PACKET_HEADROOM bytes. This is the guarantee that also > > > - * native XDP provides, thus we need to do it here as well. > > > + /* XDP does not support fraglist so we need to linearize > > > + * the skb. > > > */ > > > - if (skb_cloned(skb) || skb_is_nonlinear(skb) || > > > - skb_headroom(skb) < XDP_PACKET_HEADROOM) { > > > + if (skb_has_frag_list(skb) || !prog->aux->xdp_has_frags) { > > > int hroom = XDP_PACKET_HEADROOM - skb_headroom(skb); > > > int troom = skb->tail + skb->data_len - skb->end; > > > /* In case we have to go down the path and also linearize, > > > * then lets do the pskb_expand_head() work just once here. > > > */ > > > - if (pskb_expand_head(skb, > > > - hroom > 0 ? ALIGN(hroom, NET_SKB_PAD) : 0, > > > - troom > 0 ? troom + 128 : 0, GFP_ATOMIC)) > > > - goto do_drop; > > > - if (skb_linearize(skb)) > > > - goto do_drop; > > > + err = pskb_expand_head(skb, > > > + hroom > 0 ? ALIGN(hroom, NET_SKB_PAD) : 0, > > > + troom > 0 ? troom + 128 : 0, GFP_ATOMIC); > > > + if (err) > > > + return err; > > > + > > > + err = skb_linearize(skb); > > > + if (err) > > > + return err; > > > + > > > + return 0; > > > + } > > > + > > > + /* XDP packets must have sufficient headroom of XDP_PACKET_HEADROOM > > > + * bytes. This is the guarantee that also native XDP provides, > > > + * thus we need to do it here as well. > > > + */ > > > + if (skb_cloned(skb) || skb_shinfo(skb)->nr_frags || > > > > I though we could allow a SKB with skb_shinfo(skb)->nr_frags (that isn't > > cloned or shared) to be processed by generic XDP without any reallocation? > > I do not think so, we discussed about it with Jakub here [0] > > [0] https://lore.kernel.org/netdev/20231128105145.7b39db7d@kernel.org/ Can this be done as an optimization later on? If, from the bpf side, the verifier can attest that the program is not calling bpf_xdp_{load,store}_bytes on the frags for example.
> On 11/30, Lorenzo Bianconi wrote: > > > > > > > > > On 11/30/23 10:11, Lorenzo Bianconi wrote: > > > > Similar to native xdp, do not always linearize the skb in > > > > netif_receive_generic_xdp routine but create a non-linear xdp_buff to be > > > > processed by the eBPF program. This allow to add multi-buffer support > > > > for xdp running in generic mode. > > > > > > > > Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org> > > > > --- > > > > net/core/dev.c | 144 ++++++++++++++++++++++++++++++++++++++++--------- > > > > 1 file changed, 119 insertions(+), 25 deletions(-) > > > > > > > > diff --git a/net/core/dev.c b/net/core/dev.c > > > > index 4df68d7f04a2..0d08e755bb7f 100644 > > > > --- a/net/core/dev.c > > > > +++ b/net/core/dev.c > > > > @@ -4853,6 +4853,12 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > > > > xdp_init_buff(xdp, frame_sz, &rxqueue->xdp_rxq); > > > > xdp_prepare_buff(xdp, hard_start, skb_headroom(skb) - mac_len, > > > > skb_headlen(skb) + mac_len, true); > > > > + if (skb_is_nonlinear(skb)) { > > > > + skb_shinfo(skb)->xdp_frags_size = skb->data_len; > > > > + xdp_buff_set_frags_flag(xdp); > > > > + } else { > > > > + xdp_buff_clear_frags_flag(xdp); > > > > + } > > > > orig_data_end = xdp->data_end; > > > > orig_data = xdp->data; > > > > @@ -4882,6 +4888,14 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > > > > skb->len += off; /* positive on grow, negative on shrink */ > > > > } > > > > + /* XDP frag metadata (e.g. nr_frags) are updated in eBPF helpers > > > > + * (e.g. bpf_xdp_adjust_tail), we need to update data_len here. > > > > + */ > > > > + if (xdp_buff_has_frags(xdp)) > > > > + skb->data_len = skb_shinfo(skb)->xdp_frags_size; > > > > + else > > > > + skb->data_len = 0; > > > > + > > > > /* check if XDP changed eth hdr such SKB needs update */ > > > > eth = (struct ethhdr *)xdp->data; > > > > if ((orig_eth_type != eth->h_proto) || > > > > @@ -4915,54 +4929,134 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, > > > > return act; > > > > } > > > > -static u32 netif_receive_generic_xdp(struct sk_buff **pskb, > > > > - struct xdp_buff *xdp, > > > > - struct bpf_prog *xdp_prog) > > > > +static int netif_skb_check_for_generic_xdp(struct sk_buff **pskb, > > > > + struct bpf_prog *prog) > > > > > > I like this is split out into a check function. > > > > > > > { > > > > struct sk_buff *skb = *pskb; > > > > - u32 act = XDP_DROP; > > > > - > > > > - /* Reinjected packets coming from act_mirred or similar should > > > > - * not get XDP generic processing. > > > > - */ > > > > - if (skb_is_redirected(skb)) > > > > - return XDP_PASS; > > > > > > (For other reviewers) > > > This reinjected check is moved further down. > > > > > > > + int err; > > > > - /* XDP packets must be linear and must have sufficient headroom > > > > - * of XDP_PACKET_HEADROOM bytes. This is the guarantee that also > > > > - * native XDP provides, thus we need to do it here as well. > > > > + /* XDP does not support fraglist so we need to linearize > > > > + * the skb. > > > > */ > > > > - if (skb_cloned(skb) || skb_is_nonlinear(skb) || > > > > - skb_headroom(skb) < XDP_PACKET_HEADROOM) { > > > > + if (skb_has_frag_list(skb) || !prog->aux->xdp_has_frags) { > > > > int hroom = XDP_PACKET_HEADROOM - skb_headroom(skb); > > > > int troom = skb->tail + skb->data_len - skb->end; > > > > /* In case we have to go down the path and also linearize, > > > > * then lets do the pskb_expand_head() work just once here. > > > > */ > > > > - if (pskb_expand_head(skb, > > > > - hroom > 0 ? ALIGN(hroom, NET_SKB_PAD) : 0, > > > > - troom > 0 ? troom + 128 : 0, GFP_ATOMIC)) > > > > - goto do_drop; > > > > - if (skb_linearize(skb)) > > > > - goto do_drop; > > > > + err = pskb_expand_head(skb, > > > > + hroom > 0 ? ALIGN(hroom, NET_SKB_PAD) : 0, > > > > + troom > 0 ? troom + 128 : 0, GFP_ATOMIC); > > > > + if (err) > > > > + return err; > > > > + > > > > + err = skb_linearize(skb); > > > > + if (err) > > > > + return err; > > > > + > > > > + return 0; > > > > + } > > > > + > > > > + /* XDP packets must have sufficient headroom of XDP_PACKET_HEADROOM > > > > + * bytes. This is the guarantee that also native XDP provides, > > > > + * thus we need to do it here as well. > > > > + */ > > > > + if (skb_cloned(skb) || skb_shinfo(skb)->nr_frags || > > > > > > I though we could allow a SKB with skb_shinfo(skb)->nr_frags (that isn't > > > cloned or shared) to be processed by generic XDP without any reallocation? > > > > I do not think so, we discussed about it with Jakub here [0] > > > > [0] https://lore.kernel.org/netdev/20231128105145.7b39db7d@kernel.org/ > > Can this be done as an optimization later on? If, from the bpf side, > the verifier can attest that the program is not calling > bpf_xdp_{load,store}_bytes on the frags for example. Yes, I think so. Moreover this would be useful for veth too. Regards, Lorenzo
diff --git a/net/core/dev.c b/net/core/dev.c index 4df68d7f04a2..0d08e755bb7f 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4853,6 +4853,12 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, xdp_init_buff(xdp, frame_sz, &rxqueue->xdp_rxq); xdp_prepare_buff(xdp, hard_start, skb_headroom(skb) - mac_len, skb_headlen(skb) + mac_len, true); + if (skb_is_nonlinear(skb)) { + skb_shinfo(skb)->xdp_frags_size = skb->data_len; + xdp_buff_set_frags_flag(xdp); + } else { + xdp_buff_clear_frags_flag(xdp); + } orig_data_end = xdp->data_end; orig_data = xdp->data; @@ -4882,6 +4888,14 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, skb->len += off; /* positive on grow, negative on shrink */ } + /* XDP frag metadata (e.g. nr_frags) are updated in eBPF helpers + * (e.g. bpf_xdp_adjust_tail), we need to update data_len here. + */ + if (xdp_buff_has_frags(xdp)) + skb->data_len = skb_shinfo(skb)->xdp_frags_size; + else + skb->data_len = 0; + /* check if XDP changed eth hdr such SKB needs update */ eth = (struct ethhdr *)xdp->data; if ((orig_eth_type != eth->h_proto) || @@ -4915,54 +4929,134 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp, return act; } -static u32 netif_receive_generic_xdp(struct sk_buff **pskb, - struct xdp_buff *xdp, - struct bpf_prog *xdp_prog) +static int netif_skb_check_for_generic_xdp(struct sk_buff **pskb, + struct bpf_prog *prog) { struct sk_buff *skb = *pskb; - u32 act = XDP_DROP; - - /* Reinjected packets coming from act_mirred or similar should - * not get XDP generic processing. - */ - if (skb_is_redirected(skb)) - return XDP_PASS; + int err; - /* XDP packets must be linear and must have sufficient headroom - * of XDP_PACKET_HEADROOM bytes. This is the guarantee that also - * native XDP provides, thus we need to do it here as well. + /* XDP does not support fraglist so we need to linearize + * the skb. */ - if (skb_cloned(skb) || skb_is_nonlinear(skb) || - skb_headroom(skb) < XDP_PACKET_HEADROOM) { + if (skb_has_frag_list(skb) || !prog->aux->xdp_has_frags) { int hroom = XDP_PACKET_HEADROOM - skb_headroom(skb); int troom = skb->tail + skb->data_len - skb->end; /* In case we have to go down the path and also linearize, * then lets do the pskb_expand_head() work just once here. */ - if (pskb_expand_head(skb, - hroom > 0 ? ALIGN(hroom, NET_SKB_PAD) : 0, - troom > 0 ? troom + 128 : 0, GFP_ATOMIC)) - goto do_drop; - if (skb_linearize(skb)) - goto do_drop; + err = pskb_expand_head(skb, + hroom > 0 ? ALIGN(hroom, NET_SKB_PAD) : 0, + troom > 0 ? troom + 128 : 0, GFP_ATOMIC); + if (err) + return err; + + err = skb_linearize(skb); + if (err) + return err; + + return 0; + } + + /* XDP packets must have sufficient headroom of XDP_PACKET_HEADROOM + * bytes. This is the guarantee that also native XDP provides, + * thus we need to do it here as well. + */ + if (skb_cloned(skb) || skb_shinfo(skb)->nr_frags || + skb_headroom(skb) < XDP_PACKET_HEADROOM) { + u32 mac_len = skb->data - skb_mac_header(skb); + u32 size, len, max_head_size, off; + struct sk_buff *nskb; + int i, head_off; + + __skb_push(skb, mac_len); + max_head_size = SKB_WITH_OVERHEAD(PAGE_SIZE - + XDP_PACKET_HEADROOM); + if (skb->len > max_head_size + MAX_SKB_FRAGS * PAGE_SIZE) + return -ENOMEM; + + size = min_t(u32, skb->len, max_head_size); + nskb = netdev_alloc_skb(skb->dev, size + XDP_PACKET_HEADROOM); + if (!nskb) + return -ENOMEM; + + skb_reserve(nskb, XDP_PACKET_HEADROOM); + skb_copy_header(nskb, skb); + + err = skb_copy_bits(skb, 0, nskb->data, size); + if (err) { + consume_skb(nskb); + return err; + } + skb_put(nskb, size); + + head_off = skb_headroom(nskb) - skb_headroom(skb); + skb_headers_offset_update(nskb, head_off); + + off = size; + len = skb->len - off; + for (i = 0; i < MAX_SKB_FRAGS && off < skb->len; i++) { + struct page *page; + void *frag; + + size = min_t(u32, len, PAGE_SIZE); + frag = netdev_alloc_frag(size); + if (!frag) { + consume_skb(nskb); + return -ENOMEM; + } + + page = virt_to_head_page(frag); + skb_add_rx_frag(nskb, i, page, + frag - page_address(page), size, size); + err = skb_copy_bits(skb, off, frag, size); + if (err) { + consume_skb(nskb); + return err; + } + + len -= size; + off += size; + } + + consume_skb(skb); + *pskb = nskb; + __skb_pull(nskb, mac_len); } - act = bpf_prog_run_generic_xdp(skb, xdp, xdp_prog); + return 0; +} + +static u32 netif_receive_generic_xdp(struct sk_buff **pskb, + struct xdp_buff *xdp, + struct bpf_prog *xdp_prog) +{ + u32 act = XDP_DROP; + + /* Reinjected packets coming from act_mirred or similar should + * not get XDP generic processing. + */ + if (skb_is_redirected(*pskb)) + return XDP_PASS; + + if (netif_skb_check_for_generic_xdp(pskb, xdp_prog)) + goto do_drop; + + act = bpf_prog_run_generic_xdp(*pskb, xdp, xdp_prog); switch (act) { case XDP_REDIRECT: case XDP_TX: case XDP_PASS: break; default: - bpf_warn_invalid_xdp_action(skb->dev, xdp_prog, act); + bpf_warn_invalid_xdp_action((*pskb)->dev, xdp_prog, act); fallthrough; case XDP_ABORTED: - trace_xdp_exception(skb->dev, xdp_prog, act); + trace_xdp_exception((*pskb)->dev, xdp_prog, act); fallthrough; case XDP_DROP: do_drop: - kfree_skb(skb); + kfree_skb(*pskb); break; }
Similar to native xdp, do not always linearize the skb in netif_receive_generic_xdp routine but create a non-linear xdp_buff to be processed by the eBPF program. This allow to add multi-buffer support for xdp running in generic mode. Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org> --- net/core/dev.c | 144 ++++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 119 insertions(+), 25 deletions(-)