| Message ID | 1578031353-27654-1-git-send-email-lirongqing@baidu.com |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF Maintainers |
| Headers | show |
| Series | [bpf-next] bpf: change bpf_skb_generic_push type as void | expand |
On Fri, Jan 03, 2020 at 02:02:33PM +0800, Li RongQing wrote: > bpf_skb_generic_push always returns 0, not need to check > its return, so change its type as void > > Signed-off-by: Li RongQing <lirongqing@baidu.com> Reviewed-by: Simon Horman <simon.horman@netronome.com> > --- > net/core/filter.c | 30 ++++++++++-------------------- > 1 file changed, 10 insertions(+), 20 deletions(-) > > diff --git a/net/core/filter.c b/net/core/filter.c > index 42fd17c48c5f..1cbac34a4e11 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c ... > @@ -5144,7 +5134,7 @@ BPF_CALL_3(bpf_lwt_seg6_adjust_srh, struct sk_buff *, skb, u32, offset, > if (unlikely(ret < 0)) > return ret; > > - ret = bpf_skb_net_hdr_push(skb, offset, len); > + bpf_skb_net_hdr_push(skb, offset, len); There is a check for (ret < 0) just below this if block. That is ok becuase in order to get to here (ret < 0) must be true as per the check a few lines above. So I think this is ok although the asymmetry with the else arm of this if statement is not ideal IMHO. > } else { > ret = bpf_skb_net_hdr_pop(skb, offset, -1 * len); > } > -- > 2.16.2 >
On Fri, Jan 3, 2020 at 12:27 AM Simon Horman <simon.horman@netronome.com> wrote: > > On Fri, Jan 03, 2020 at 02:02:33PM +0800, Li RongQing wrote: > > bpf_skb_generic_push always returns 0, not need to check > > its return, so change its type as void > > > > Signed-off-by: Li RongQing <lirongqing@baidu.com> > > Reviewed-by: Simon Horman <simon.horman@netronome.com> Acked-by: Song Liu <songliubraving@fb.com> > > > --- > > net/core/filter.c | 30 ++++++++++-------------------- > > 1 file changed, 10 insertions(+), 20 deletions(-) > > > > diff --git a/net/core/filter.c b/net/core/filter.c > > index 42fd17c48c5f..1cbac34a4e11 100644 > > --- a/net/core/filter.c > > +++ b/net/core/filter.c > > ... > > > @@ -5144,7 +5134,7 @@ BPF_CALL_3(bpf_lwt_seg6_adjust_srh, struct sk_buff *, skb, u32, offset, > > if (unlikely(ret < 0)) > > return ret; > > > > - ret = bpf_skb_net_hdr_push(skb, offset, len); > > + bpf_skb_net_hdr_push(skb, offset, len); > > There is a check for (ret < 0) just below this if block. > That is ok becuase in order to get to here (ret < 0) must > be true as per the check a few lines above. > > So I think this is ok although the asymmetry with the else arm > of this if statement is not ideal IMHO. Agreed with this concern. But I cannot think of any free solution. I guess we will just live with assumption that skb_cow_head() never return >0. Thanks, Song
On Fri, Jan 03, 2020 at 11:18:28AM -0800, Song Liu wrote: > On Fri, Jan 3, 2020 at 12:27 AM Simon Horman <simon.horman@netronome.com> wrote: > > > > On Fri, Jan 03, 2020 at 02:02:33PM +0800, Li RongQing wrote: > > > bpf_skb_generic_push always returns 0, not need to check > > > its return, so change its type as void > > > > > > Signed-off-by: Li RongQing <lirongqing@baidu.com> > > > > Reviewed-by: Simon Horman <simon.horman@netronome.com> > Acked-by: Song Liu <songliubraving@fb.com> > > > > > > --- > > > net/core/filter.c | 30 ++++++++++-------------------- > > > 1 file changed, 10 insertions(+), 20 deletions(-) > > > > > > diff --git a/net/core/filter.c b/net/core/filter.c > > > index 42fd17c48c5f..1cbac34a4e11 100644 > > > --- a/net/core/filter.c > > > +++ b/net/core/filter.c > > > > ... > > > > > @@ -5144,7 +5134,7 @@ BPF_CALL_3(bpf_lwt_seg6_adjust_srh, struct sk_buff *, skb, u32, offset, > > > if (unlikely(ret < 0)) > > > return ret; > > > > > > - ret = bpf_skb_net_hdr_push(skb, offset, len); > > > + bpf_skb_net_hdr_push(skb, offset, len); > > > > There is a check for (ret < 0) just below this if block. > > That is ok becuase in order to get to here (ret < 0) must > > be true as per the check a few lines above. > > > > So I think this is ok although the asymmetry with the else arm > > of this if statement is not ideal IMHO. > > Agreed with this concern. But I cannot think of any free solution. I guess we > will just live with assumption that skb_cow_head() never return >0. I don't think this patch is worth doing. I can imagine bpf_skb_generic_push() handling some errors in the future. compiler can do this optimization job instead.
On 1/6/20 11:32 PM, Alexei Starovoitov wrote: > On Fri, Jan 03, 2020 at 11:18:28AM -0800, Song Liu wrote: >> On Fri, Jan 3, 2020 at 12:27 AM Simon Horman <simon.horman@netronome.com> wrote: >>> On Fri, Jan 03, 2020 at 02:02:33PM +0800, Li RongQing wrote: >>>> bpf_skb_generic_push always returns 0, not need to check >>>> its return, so change its type as void >>>> >>>> Signed-off-by: Li RongQing <lirongqing@baidu.com> >>> >>> Reviewed-by: Simon Horman <simon.horman@netronome.com> >> Acked-by: Song Liu <songliubraving@fb.com> >> >>> >>>> --- >>>> net/core/filter.c | 30 ++++++++++-------------------- >>>> 1 file changed, 10 insertions(+), 20 deletions(-) >>>> >>>> diff --git a/net/core/filter.c b/net/core/filter.c >>>> index 42fd17c48c5f..1cbac34a4e11 100644 >>>> --- a/net/core/filter.c >>>> +++ b/net/core/filter.c >>> >>> ... >>> >>>> @@ -5144,7 +5134,7 @@ BPF_CALL_3(bpf_lwt_seg6_adjust_srh, struct sk_buff *, skb, u32, offset, >>>> if (unlikely(ret < 0)) >>>> return ret; >>>> >>>> - ret = bpf_skb_net_hdr_push(skb, offset, len); >>>> + bpf_skb_net_hdr_push(skb, offset, len); >>> >>> There is a check for (ret < 0) just below this if block. >>> That is ok becuase in order to get to here (ret < 0) must >>> be true as per the check a few lines above. >>> >>> So I think this is ok although the asymmetry with the else arm >>> of this if statement is not ideal IMHO. >> >> Agreed with this concern. But I cannot think of any free solution. I guess we >> will just live with assumption that skb_cow_head() never return >0. > > I don't think this patch is worth doing. > I can imagine bpf_skb_generic_push() handling some errors in the future. > compiler can do this optimization job instead. Yep, fully agree.
diff --git a/net/core/filter.c b/net/core/filter.c index 42fd17c48c5f..1cbac34a4e11 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2761,7 +2761,7 @@ static const struct bpf_func_proto bpf_skb_vlan_pop_proto = { .arg1_type = ARG_PTR_TO_CTX, }; -static int bpf_skb_generic_push(struct sk_buff *skb, u32 off, u32 len) +static void bpf_skb_generic_push(struct sk_buff *skb, u32 off, u32 len) { /* Caller already did skb_cow() with len as headroom, * so no need to do it here. @@ -2775,7 +2775,6 @@ static int bpf_skb_generic_push(struct sk_buff *skb, u32 off, u32 len) * result for checksum complete when summing over * zeroed blocks. */ - return 0; } static int bpf_skb_generic_pop(struct sk_buff *skb, u32 off, u32 len) @@ -2793,24 +2792,19 @@ static int bpf_skb_generic_pop(struct sk_buff *skb, u32 off, u32 len) return 0; } -static int bpf_skb_net_hdr_push(struct sk_buff *skb, u32 off, u32 len) +static void bpf_skb_net_hdr_push(struct sk_buff *skb, u32 off, u32 len) { bool trans_same = skb->transport_header == skb->network_header; - int ret; /* There's no need for __skb_push()/__skb_pull() pair to * get to the start of the mac header as we're guaranteed * to always start from here under eBPF. */ - ret = bpf_skb_generic_push(skb, off, len); - if (likely(!ret)) { - skb->mac_header -= len; - skb->network_header -= len; - if (trans_same) - skb->transport_header = skb->network_header; - } - - return ret; + bpf_skb_generic_push(skb, off, len); + skb->mac_header -= len; + skb->network_header -= len; + if (trans_same) + skb->transport_header = skb->network_header; } static int bpf_skb_net_hdr_pop(struct sk_buff *skb, u32 off, u32 len) @@ -2843,9 +2837,7 @@ static int bpf_skb_proto_4_to_6(struct sk_buff *skb) if (unlikely(ret < 0)) return ret; - ret = bpf_skb_net_hdr_push(skb, off, len_diff); - if (unlikely(ret < 0)) - return ret; + bpf_skb_net_hdr_push(skb, off, len_diff); if (skb_is_gso(skb)) { struct skb_shared_info *shinfo = skb_shinfo(skb); @@ -3050,9 +3042,7 @@ static int bpf_skb_net_grow(struct sk_buff *skb, u32 off, u32 len_diff, inner_trans = skb->transport_header; } - ret = bpf_skb_net_hdr_push(skb, off, len_diff); - if (unlikely(ret < 0)) - return ret; + bpf_skb_net_hdr_push(skb, off, len_diff); if (encap) { skb->inner_mac_header = inner_net - inner_mac_len; @@ -5144,7 +5134,7 @@ BPF_CALL_3(bpf_lwt_seg6_adjust_srh, struct sk_buff *, skb, u32, offset, if (unlikely(ret < 0)) return ret; - ret = bpf_skb_net_hdr_push(skb, offset, len); + bpf_skb_net_hdr_push(skb, offset, len); } else { ret = bpf_skb_net_hdr_pop(skb, offset, -1 * len); }
bpf_skb_generic_push always returns 0, not need to check its return, so change its type as void Signed-off-by: Li RongQing <lirongqing@baidu.com> --- net/core/filter.c | 30 ++++++++++-------------------- 1 file changed, 10 insertions(+), 20 deletions(-)