tc: bpf: add checksum helpers
Commit 608cd71a9c ("tc: bpf: generalize pedit action") has added the
possibility to mangle packet data to BPF programs in the tc pipeline.
This patch adds two helpers bpf_l3_csum_replace() and bpf_l4_csum_replace()
for fixing up the protocol checksums after the packet mangling.
It also adds 'flags' argument to bpf_skb_store_bytes() helper to avoid
unnecessary checksum recomputations when BPF programs adjusting l3/l4
checksums and documents all three helpers in uapi header.
Moreover, a sample program is added to show how BPF programs can make use
of the mangle and csum helpers.
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Alexei Starovoitov
David S. Miller
Родитель
5888b93b75
Коммит
91bc4822c3
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@ -168,7 +168,43 @@ enum bpf_func_id {
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BPF_FUNC_map_delete_elem, /* int map_delete_elem(&map, &key) */
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BPF_FUNC_get_prandom_u32, /* u32 prandom_u32(void) */
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BPF_FUNC_get_smp_processor_id, /* u32 raw_smp_processor_id(void) */
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BPF_FUNC_skb_store_bytes, /* int skb_store_bytes(skb, offset, from, len) */
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/**
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* skb_store_bytes(skb, offset, from, len, flags) - store bytes into packet
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* @skb: pointer to skb
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* @offset: offset within packet from skb->data
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* @from: pointer where to copy bytes from
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* @len: number of bytes to store into packet
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* @flags: bit 0 - if true, recompute skb->csum
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* other bits - reserved
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* Return: 0 on success
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*/
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BPF_FUNC_skb_store_bytes,
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/**
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* l3_csum_replace(skb, offset, from, to, flags) - recompute IP checksum
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* @skb: pointer to skb
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* @offset: offset within packet where IP checksum is located
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* @from: old value of header field
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* @to: new value of header field
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* @flags: bits 0-3 - size of header field
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* other bits - reserved
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* Return: 0 on success
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*/
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BPF_FUNC_l3_csum_replace,
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/**
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* l4_csum_replace(skb, offset, from, to, flags) - recompute TCP/UDP checksum
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* @skb: pointer to skb
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* @offset: offset within packet where TCP/UDP checksum is located
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* @from: old value of header field
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* @to: new value of header field
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* @flags: bits 0-3 - size of header field
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* bit 4 - is pseudo header
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* other bits - reserved
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* Return: 0 on success
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*/
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BPF_FUNC_l4_csum_replace,
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__BPF_FUNC_MAX_ID,
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};
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@ -1175,7 +1175,9 @@ int sk_attach_bpf(u32 ufd, struct sock *sk)
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return 0;
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}
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static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
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#define BPF_RECOMPUTE_CSUM(flags) ((flags) & 1)
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static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 flags)
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{
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struct sk_buff *skb = (struct sk_buff *) (long) r1;
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unsigned int offset = (unsigned int) r2;
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@ -1192,7 +1194,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
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*
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* so check for invalid 'offset' and too large 'len'
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*/
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if (offset > 0xffff || len > sizeof(buf))
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if (unlikely(offset > 0xffff || len > sizeof(buf)))
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return -EFAULT;
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if (skb_cloned(skb) && !skb_clone_writable(skb, offset + len))
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@ -1202,6 +1204,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
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if (unlikely(!ptr))
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return -EFAULT;
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if (BPF_RECOMPUTE_CSUM(flags))
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skb_postpull_rcsum(skb, ptr, len);
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memcpy(ptr, from, len);
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@ -1210,7 +1213,7 @@ static u64 bpf_skb_store_bytes(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
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/* skb_store_bits cannot return -EFAULT here */
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skb_store_bits(skb, offset, ptr, len);
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if (skb->ip_summed == CHECKSUM_COMPLETE)
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if (BPF_RECOMPUTE_CSUM(flags) && skb->ip_summed == CHECKSUM_COMPLETE)
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skb->csum = csum_add(skb->csum, csum_partial(ptr, len, 0));
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return 0;
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}
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@ -1223,6 +1226,99 @@ const struct bpf_func_proto bpf_skb_store_bytes_proto = {
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.arg2_type = ARG_ANYTHING,
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.arg3_type = ARG_PTR_TO_STACK,
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.arg4_type = ARG_CONST_STACK_SIZE,
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.arg5_type = ARG_ANYTHING,
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};
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#define BPF_HEADER_FIELD_SIZE(flags) ((flags) & 0x0f)
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#define BPF_IS_PSEUDO_HEADER(flags) ((flags) & 0x10)
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static u64 bpf_l3_csum_replace(u64 r1, u64 offset, u64 from, u64 to, u64 flags)
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{
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struct sk_buff *skb = (struct sk_buff *) (long) r1;
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__sum16 sum, *ptr;
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if (unlikely(offset > 0xffff))
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return -EFAULT;
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if (skb_cloned(skb) && !skb_clone_writable(skb, offset + sizeof(sum)))
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return -EFAULT;
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ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
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if (unlikely(!ptr))
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return -EFAULT;
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switch (BPF_HEADER_FIELD_SIZE(flags)) {
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case 2:
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csum_replace2(ptr, from, to);
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break;
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case 4:
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csum_replace4(ptr, from, to);
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break;
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default:
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return -EINVAL;
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}
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if (ptr == &sum)
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/* skb_store_bits guaranteed to not return -EFAULT here */
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skb_store_bits(skb, offset, ptr, sizeof(sum));
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return 0;
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}
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const struct bpf_func_proto bpf_l3_csum_replace_proto = {
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.func = bpf_l3_csum_replace,
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.gpl_only = false,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_PTR_TO_CTX,
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.arg2_type = ARG_ANYTHING,
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.arg3_type = ARG_ANYTHING,
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.arg4_type = ARG_ANYTHING,
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.arg5_type = ARG_ANYTHING,
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};
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static u64 bpf_l4_csum_replace(u64 r1, u64 offset, u64 from, u64 to, u64 flags)
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{
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struct sk_buff *skb = (struct sk_buff *) (long) r1;
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u32 is_pseudo = BPF_IS_PSEUDO_HEADER(flags);
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__sum16 sum, *ptr;
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if (unlikely(offset > 0xffff))
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return -EFAULT;
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if (skb_cloned(skb) && !skb_clone_writable(skb, offset + sizeof(sum)))
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return -EFAULT;
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ptr = skb_header_pointer(skb, offset, sizeof(sum), &sum);
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if (unlikely(!ptr))
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return -EFAULT;
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switch (BPF_HEADER_FIELD_SIZE(flags)) {
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case 2:
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inet_proto_csum_replace2(ptr, skb, from, to, is_pseudo);
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break;
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case 4:
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inet_proto_csum_replace4(ptr, skb, from, to, is_pseudo);
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break;
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default:
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return -EINVAL;
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}
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if (ptr == &sum)
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/* skb_store_bits guaranteed to not return -EFAULT here */
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skb_store_bits(skb, offset, ptr, sizeof(sum));
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return 0;
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}
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const struct bpf_func_proto bpf_l4_csum_replace_proto = {
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.func = bpf_l4_csum_replace,
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.gpl_only = false,
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.ret_type = RET_INTEGER,
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.arg1_type = ARG_PTR_TO_CTX,
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.arg2_type = ARG_ANYTHING,
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.arg3_type = ARG_ANYTHING,
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.arg4_type = ARG_ANYTHING,
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.arg5_type = ARG_ANYTHING,
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};
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static const struct bpf_func_proto *
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@ -1250,6 +1346,10 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
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switch (func_id) {
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case BPF_FUNC_skb_store_bytes:
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return &bpf_skb_store_bytes_proto;
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case BPF_FUNC_l3_csum_replace:
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return &bpf_l3_csum_replace_proto;
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case BPF_FUNC_l4_csum_replace:
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return &bpf_l4_csum_replace_proto;
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default:
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return sk_filter_func_proto(func_id);
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}
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@ -17,6 +17,7 @@ sockex2-objs := bpf_load.o libbpf.o sockex2_user.o
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always := $(hostprogs-y)
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always += sockex1_kern.o
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always += sockex2_kern.o
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always += tcbpf1_kern.o
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HOSTCFLAGS += -I$(objtree)/usr/include
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@ -37,4 +37,11 @@ struct bpf_map_def {
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unsigned int max_entries;
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};
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static int (*bpf_skb_store_bytes)(void *ctx, int off, void *from, int len, int flags) =
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(void *) BPF_FUNC_skb_store_bytes;
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static int (*bpf_l3_csum_replace)(void *ctx, int off, int from, int to, int flags) =
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(void *) BPF_FUNC_l3_csum_replace;
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static int (*bpf_l4_csum_replace)(void *ctx, int off, int from, int to, int flags) =
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(void *) BPF_FUNC_l4_csum_replace;
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#endif
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@ -0,0 +1,71 @@
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#include <uapi/linux/bpf.h>
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#include <uapi/linux/if_ether.h>
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#include <uapi/linux/if_packet.h>
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#include <uapi/linux/ip.h>
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#include <uapi/linux/in.h>
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#include <uapi/linux/tcp.h>
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#include "bpf_helpers.h"
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/* compiler workaround */
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#define _htonl __builtin_bswap32
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static inline void set_dst_mac(struct __sk_buff *skb, char *mac)
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{
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bpf_skb_store_bytes(skb, 0, mac, ETH_ALEN, 1);
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}
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/* use 1 below for ingress qdisc and 0 for egress */
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#if 0
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#undef ETH_HLEN
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#define ETH_HLEN 0
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#endif
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#define IP_CSUM_OFF (ETH_HLEN + offsetof(struct iphdr, check))
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#define TOS_OFF (ETH_HLEN + offsetof(struct iphdr, tos))
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static inline void set_ip_tos(struct __sk_buff *skb, __u8 new_tos)
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{
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__u8 old_tos = load_byte(skb, TOS_OFF);
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bpf_l3_csum_replace(skb, IP_CSUM_OFF, htons(old_tos), htons(new_tos), 2);
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bpf_skb_store_bytes(skb, TOS_OFF, &new_tos, sizeof(new_tos), 0);
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}
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#define TCP_CSUM_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, check))
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#define IP_SRC_OFF (ETH_HLEN + offsetof(struct iphdr, saddr))
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#define IS_PSEUDO 0x10
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static inline void set_tcp_ip_src(struct __sk_buff *skb, __u32 new_ip)
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{
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__u32 old_ip = _htonl(load_word(skb, IP_SRC_OFF));
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bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_ip, new_ip, IS_PSEUDO | sizeof(new_ip));
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bpf_l3_csum_replace(skb, IP_CSUM_OFF, old_ip, new_ip, sizeof(new_ip));
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bpf_skb_store_bytes(skb, IP_SRC_OFF, &new_ip, sizeof(new_ip), 0);
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}
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#define TCP_DPORT_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, dest))
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static inline void set_tcp_dest_port(struct __sk_buff *skb, __u16 new_port)
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{
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__u16 old_port = htons(load_half(skb, TCP_DPORT_OFF));
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bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_port, new_port, sizeof(new_port));
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bpf_skb_store_bytes(skb, TCP_DPORT_OFF, &new_port, sizeof(new_port), 0);
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}
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SEC("classifier")
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int bpf_prog1(struct __sk_buff *skb)
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{
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__u8 proto = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
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long *value;
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if (proto == IPPROTO_TCP) {
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set_ip_tos(skb, 8);
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set_tcp_ip_src(skb, 0xA010101);
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set_tcp_dest_port(skb, 5001);
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}
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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