Message ID | 20180417065131.3632-2-tehnerd@tehnerd.com |
---|---|
State | Changes Requested, archived |
Delegated to: | BPF Maintainers |
Headers | show |
Series | introduction of bpf_xdp_adjust_tail | expand |
Hi Nikita, Thank you for the patch! Perhaps something to improve: [auto build test WARNING on bpf-next/master] url: https://github.com/0day-ci/linux/commits/Nikita-V-Shirokov/introduction-of-bpf_xdp_adjust_tail/20180417-211905 base: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git master config: i386-randconfig-s1-201815 (attached as .config) compiler: gcc-6 (Debian 6.4.0-9) 6.4.0 20171026 reproduce: # save the attached .config to linux build tree make ARCH=i386 All warnings (new ones prefixed by >>): net/core/filter.c: In function '____bpf_xdp_adjust_tail': >> net/core/filter.c:2726:2: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement] void *data_end = xdp->data_end + offset; ^~~~ vim +2726 net/core/filter.c 2719 2720 BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset) 2721 { 2722 /* only shrinking is allowed for now. */ 2723 if (unlikely(offset > 0)) 2724 return -EINVAL; 2725 > 2726 void *data_end = xdp->data_end + offset; 2727 2728 if (unlikely(data_end < xdp->data + ETH_HLEN)) 2729 return -EINVAL; 2730 2731 xdp->data_end = data_end; 2732 2733 return 0; 2734 } 2735 --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
On Mon, Apr 16, 2018 at 11:51:22PM -0700, Nikita V. Shirokov wrote: > Adding new bpf helper which would allow us to manipulate > xdp's data_end pointer, and allow us to reduce packet's size > indended use case: to generate ICMP messages from XDP context, > where such message would contain truncated original packet. > > Signed-off-by: Nikita V. Shirokov <tehnerd@tehnerd.com> > --- > include/uapi/linux/bpf.h | 10 +++++++++- > net/core/filter.c | 29 ++++++++++++++++++++++++++++- > 2 files changed, 37 insertions(+), 2 deletions(-) > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > index c5ec89732a8d..9a2d1a04eb24 100644 > --- a/include/uapi/linux/bpf.h > +++ b/include/uapi/linux/bpf.h > @@ -755,6 +755,13 @@ union bpf_attr { > * @addr: pointer to struct sockaddr to bind socket to > * @addr_len: length of sockaddr structure > * Return: 0 on success or negative error code > + * > + * int bpf_xdp_adjust_tail(xdp_md, delta) > + * Adjust the xdp_md.data_end by delta. Only shrinking of packet's > + * size is supported. > + * @xdp_md: pointer to xdp_md > + * @delta: A negative integer to be added to xdp_md.data_end > + * Return: 0 on success or negative on error > */ > #define __BPF_FUNC_MAPPER(FN) \ > FN(unspec), \ > @@ -821,7 +828,8 @@ union bpf_attr { > FN(msg_apply_bytes), \ > FN(msg_cork_bytes), \ > FN(msg_pull_data), \ > - FN(bind), > + FN(bind), \ > + FN(xdp_adjust_tail), > > /* integer value in 'imm' field of BPF_CALL instruction selects which helper > * function eBPF program intends to call > diff --git a/net/core/filter.c b/net/core/filter.c > index d31aff93270d..6c8ac7b548d6 100644 > --- a/net/core/filter.c > +++ b/net/core/filter.c > @@ -2717,6 +2717,30 @@ static const struct bpf_func_proto bpf_xdp_adjust_head_proto = { > .arg2_type = ARG_ANYTHING, > }; > > +BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset) > +{ > + /* only shrinking is allowed for now. */ > + if (unlikely(offset > 0)) > + return -EINVAL; why allow offset == 0 ? It's a nop. xdp_adjust_head allows it, but it's not a reason to repeat the same here. Like we may decide to do something with offset==0 in the future. Let's keep it reserved. In the subject please replace [bpf]: adding bpf_xdp_adjust_tail helper with bpf: adding bpf_xdp_adjust_tail helper "[bpf] foo bar" subject used to be llvm patch convention, but lately we switched it to kernel style as well with "bpf: foo bar"
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index c5ec89732a8d..9a2d1a04eb24 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -755,6 +755,13 @@ union bpf_attr { * @addr: pointer to struct sockaddr to bind socket to * @addr_len: length of sockaddr structure * Return: 0 on success or negative error code + * + * int bpf_xdp_adjust_tail(xdp_md, delta) + * Adjust the xdp_md.data_end by delta. Only shrinking of packet's + * size is supported. + * @xdp_md: pointer to xdp_md + * @delta: A negative integer to be added to xdp_md.data_end + * Return: 0 on success or negative on error */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -821,7 +828,8 @@ union bpf_attr { FN(msg_apply_bytes), \ FN(msg_cork_bytes), \ FN(msg_pull_data), \ - FN(bind), + FN(bind), \ + FN(xdp_adjust_tail), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call diff --git a/net/core/filter.c b/net/core/filter.c index d31aff93270d..6c8ac7b548d6 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2717,6 +2717,30 @@ static const struct bpf_func_proto bpf_xdp_adjust_head_proto = { .arg2_type = ARG_ANYTHING, }; +BPF_CALL_2(bpf_xdp_adjust_tail, struct xdp_buff *, xdp, int, offset) +{ + /* only shrinking is allowed for now. */ + if (unlikely(offset > 0)) + return -EINVAL; + + void *data_end = xdp->data_end + offset; + + if (unlikely(data_end < xdp->data + ETH_HLEN)) + return -EINVAL; + + xdp->data_end = data_end; + + return 0; +} + +static const struct bpf_func_proto bpf_xdp_adjust_tail_proto = { + .func = bpf_xdp_adjust_tail, + .gpl_only = false, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_ANYTHING, +}; + BPF_CALL_2(bpf_xdp_adjust_meta, struct xdp_buff *, xdp, int, offset) { void *meta = xdp->data_meta + offset; @@ -3053,7 +3077,8 @@ bool bpf_helper_changes_pkt_data(void *func) func == bpf_l4_csum_replace || func == bpf_xdp_adjust_head || func == bpf_xdp_adjust_meta || - func == bpf_msg_pull_data) + func == bpf_msg_pull_data || + func == bpf_xdp_adjust_tail) return true; return false; @@ -3867,6 +3892,8 @@ xdp_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_xdp_redirect_proto; case BPF_FUNC_redirect_map: return &bpf_xdp_redirect_map_proto; + case BPF_FUNC_xdp_adjust_tail: + return &bpf_xdp_adjust_tail_proto; default: return bpf_base_func_proto(func_id); }
Adding new bpf helper which would allow us to manipulate xdp's data_end pointer, and allow us to reduce packet's size indended use case: to generate ICMP messages from XDP context, where such message would contain truncated original packet. Signed-off-by: Nikita V. Shirokov <tehnerd@tehnerd.com> --- include/uapi/linux/bpf.h | 10 +++++++++- net/core/filter.c | 29 ++++++++++++++++++++++++++++- 2 files changed, 37 insertions(+), 2 deletions(-)