bpf: Add __sk_buff->delivery_time_type and bpf_skb_set_skb_delivery_time()

* __sk_buff->delivery_time_type:
This patch adds __sk_buff->delivery_time_type.  It tells if the
delivery_time is stored in __sk_buff->tstamp or not.

It will be most useful for ingress to tell if the __sk_buff->tstamp
has the (rcv) timestamp or delivery_time.  If delivery_time_type
is 0 (BPF_SKB_DELIVERY_TIME_NONE), it has the (rcv) timestamp.

Two non-zero types are defined for the delivery_time_type,
BPF_SKB_DELIVERY_TIME_MONO and BPF_SKB_DELIVERY_TIME_UNSPEC.  For UNSPEC,
it can only happen in egress because only mono delivery_time can be
forwarded to ingress now.  The clock of UNSPEC delivery_time
can be deduced from the skb->sk->sk_clockid which is how
the sch_etf doing it also.

* Provide forwarded delivery_time to tc-bpf@ingress:
With the help of the new delivery_time_type, the tc-bpf has a way
to tell if the __sk_buff->tstamp has the (rcv) timestamp or
the delivery_time.  During bpf load time, the verifier will learn if
the bpf prog has accessed the new __sk_buff->delivery_time_type.
If it does, it means the tc-bpf@ingress is expecting the
skb->tstamp could have the delivery_time.  The kernel will then
read the skb->tstamp as-is during bpf insn rewrite without
checking the skb->mono_delivery_time.  This is done by adding a
new prog->delivery_time_access bit.  The same goes for
writing skb->tstamp.

* bpf_skb_set_delivery_time():
The bpf_skb_set_delivery_time() helper is added to allow setting both
delivery_time and the delivery_time_type at the same time.  If the
tc-bpf does not need to change the delivery_time_type, it can directly
write to the __sk_buff->tstamp as the existing tc-bpf has already been
doing.  It will be most useful at ingress to change the
__sk_buff->tstamp from the (rcv) timestamp to
a mono delivery_time and then bpf_redirect_*().

bpf only has mono clock helper (bpf_ktime_get_ns), and
the current known use case is the mono EDT for fq, and
only mono delivery time can be kept during forward now,
so bpf_skb_set_delivery_time() only supports setting
BPF_SKB_DELIVERY_TIME_MONO.  It can be extended later when use cases
come up and the forwarding path also supports other clock bases.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 1cb1af9..9bf2630 100644 (file)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -572,7 +572,8 @@ struct bpf_prog {
                                has_callchain_buf:1, /* callchain buffer allocated? */
                                enforce_expected_attach_type:1, /* Enforce expected_attach_type checking at attach time */
                                call_get_stack:1, /* Do we call bpf_get_stack() or bpf_get_stackid() */
-                               call_get_func_ip:1; /* Do we call get_func_ip() */
+                               call_get_func_ip:1, /* Do we call get_func_ip() */
+                               delivery_time_access:1; /* Accessed __sk_buff->delivery_time_type */
        enum bpf_prog_type      type;           /* Type of BPF program */
        enum bpf_attach_type    expected_attach_type; /* For some prog types */
        u32                     len;            /* Number of filter blocks */

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index afe3d0d..4eebea8 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5086,6 +5086,37 @@ union bpf_attr {
  *     Return
  *             0 on success, or a negative error in case of failure. On error
  *             *dst* buffer is zeroed out.
+ *
+ * long bpf_skb_set_delivery_time(struct sk_buff *skb, u64 dtime, u32 dtime_type)
+ *     Description
+ *             Set a *dtime* (delivery time) to the __sk_buff->tstamp and also
+ *             change the __sk_buff->delivery_time_type to *dtime_type*.
+ *
+ *             When setting a delivery time (non zero *dtime*) to
+ *             __sk_buff->tstamp, only BPF_SKB_DELIVERY_TIME_MONO *dtime_type*
+ *             is supported.  It is the only delivery_time_type that will be
+ *             kept after bpf_redirect_*().
+ *
+ *             If there is no need to change the __sk_buff->delivery_time_type,
+ *             the delivery time can be directly written to __sk_buff->tstamp
+ *             instead.
+ *
+ *             *dtime* 0 and *dtime_type* BPF_SKB_DELIVERY_TIME_NONE
+ *             can be used to clear any delivery time stored in
+ *             __sk_buff->tstamp.
+ *
+ *             Only IPv4 and IPv6 skb->protocol are supported.
+ *
+ *             This function is most useful when it needs to set a
+ *             mono delivery time to __sk_buff->tstamp and then
+ *             bpf_redirect_*() to the egress of an iface.  For example,
+ *             changing the (rcv) timestamp in __sk_buff->tstamp at
+ *             ingress to a mono delivery time and then bpf_redirect_*()
+ *             to sch_fq@phy-dev.
+ *     Return
+ *             0 on success.
+ *             **-EINVAL** for invalid input
+ *             **-EOPNOTSUPP** for unsupported delivery_time_type and protocol
  */
 #define __BPF_FUNC_MAPPER(FN)          \
        FN(unspec),                     \
@@ -5280,6 +5311,7 @@ union bpf_attr {
        FN(xdp_load_bytes),             \
        FN(xdp_store_bytes),            \
        FN(copy_from_user_task),        \
+       FN(skb_set_delivery_time),      \
        /* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
@@ -5469,6 +5501,12 @@ union {                                  \
        __u64 :64;                      \
 } __attribute__((aligned(8)))
 
+enum {
+       BPF_SKB_DELIVERY_TIME_NONE,
+       BPF_SKB_DELIVERY_TIME_UNSPEC,
+       BPF_SKB_DELIVERY_TIME_MONO,
+};
+
 /* user accessible mirror of in-kernel sk_buff.
  * new fields can only be added to the end of this structure
  */
@@ -5509,7 +5547,8 @@ struct __sk_buff {
        __u32 gso_segs;
        __bpf_md_ptr(struct bpf_sock *, sk);
        __u32 gso_size;
-       __u32 :32;              /* Padding, future use. */
+       __u8  delivery_time_type;
+       __u32 :24;              /* Padding, future use. */
        __u64 hwtstamp;
 };
 

diff --git a/net/core/filter.c b/net/core/filter.c
index 5072733..88767f7 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -7388,6 +7388,43 @@ static const struct bpf_func_proto bpf_sock_ops_reserve_hdr_opt_proto = {
        .arg3_type      = ARG_ANYTHING,
 };
 
+BPF_CALL_3(bpf_skb_set_delivery_time, struct sk_buff *, skb,
+          u64, dtime, u32, dtime_type)
+{
+       /* skb_clear_delivery_time() is done for inet protocol */
+       if (skb->protocol != htons(ETH_P_IP) &&
+           skb->protocol != htons(ETH_P_IPV6))
+               return -EOPNOTSUPP;
+
+       switch (dtime_type) {
+       case BPF_SKB_DELIVERY_TIME_MONO:
+               if (!dtime)
+                       return -EINVAL;
+               skb->tstamp = dtime;
+               skb->mono_delivery_time = 1;
+               break;
+       case BPF_SKB_DELIVERY_TIME_NONE:
+               if (dtime)
+                       return -EINVAL;
+               skb->tstamp = 0;
+               skb->mono_delivery_time = 0;
+               break;
+       default:
+               return -EOPNOTSUPP;
+       }
+
+       return 0;
+}
+
+static const struct bpf_func_proto bpf_skb_set_delivery_time_proto = {
+       .func           = bpf_skb_set_delivery_time,
+       .gpl_only       = false,
+       .ret_type       = RET_INTEGER,
+       .arg1_type      = ARG_PTR_TO_CTX,
+       .arg2_type      = ARG_ANYTHING,
+       .arg3_type      = ARG_ANYTHING,
+};
+
 #endif /* CONFIG_INET */
 
 bool bpf_helper_changes_pkt_data(void *func)
@@ -7749,6 +7786,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
                return &bpf_tcp_gen_syncookie_proto;
        case BPF_FUNC_sk_assign:
                return &bpf_sk_assign_proto;
+       case BPF_FUNC_skb_set_delivery_time:
+               return &bpf_skb_set_delivery_time_proto;
 #endif
        default:
                return bpf_sk_base_func_proto(func_id);
@@ -8088,7 +8127,9 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type
                        return false;
                info->reg_type = PTR_TO_SOCK_COMMON_OR_NULL;
                break;
-       case offsetofend(struct __sk_buff, gso_size) ... offsetof(struct __sk_buff, hwtstamp) - 1:
+       case offsetof(struct __sk_buff, delivery_time_type):
+               return false;
+       case offsetofend(struct __sk_buff, delivery_time_type) ... offsetof(struct __sk_buff, hwtstamp) - 1:
                /* Explicitly prohibit access to padding in __sk_buff. */
                return false;
        default:
@@ -8443,6 +8484,15 @@ static bool tc_cls_act_is_valid_access(int off, int size,
                break;
        case bpf_ctx_range_till(struct __sk_buff, family, local_port):
                return false;
+       case offsetof(struct __sk_buff, delivery_time_type):
+               /* The convert_ctx_access() on reading and writing
+                * __sk_buff->tstamp depends on whether the bpf prog
+                * has used __sk_buff->delivery_time_type or not.
+                * Thus, we need to set prog->delivery_time_access
+                * earlier during is_valid_access() here.
+                */
+               ((struct bpf_prog *)prog)->delivery_time_access = 1;
+               return size == sizeof(__u8);
        }
 
        return bpf_skb_is_valid_access(off, size, type, prog, info);
@@ -8838,6 +8888,45 @@ static u32 flow_dissector_convert_ctx_access(enum bpf_access_type type,
        return insn - insn_buf;
 }
 
+static struct bpf_insn *bpf_convert_dtime_type_read(const struct bpf_insn *si,
+                                                   struct bpf_insn *insn)
+{
+       __u8 value_reg = si->dst_reg;
+       __u8 skb_reg = si->src_reg;
+       __u8 tmp_reg = BPF_REG_AX;
+
+       *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
+                             SKB_MONO_DELIVERY_TIME_OFFSET);
+       *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
+                               SKB_MONO_DELIVERY_TIME_MASK);
+       *insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 2);
+       /* value_reg = BPF_SKB_DELIVERY_TIME_MONO */
+       *insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_DELIVERY_TIME_MONO);
+       *insn++ = BPF_JMP_A(IS_ENABLED(CONFIG_NET_CLS_ACT) ? 10 : 5);
+
+       *insn++ = BPF_LDX_MEM(BPF_DW, tmp_reg, skb_reg,
+                             offsetof(struct sk_buff, tstamp));
+       *insn++ = BPF_JMP_IMM(BPF_JNE, tmp_reg, 0, 2);
+       /* value_reg = BPF_SKB_DELIVERY_TIME_NONE */
+       *insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_DELIVERY_TIME_NONE);
+       *insn++ = BPF_JMP_A(IS_ENABLED(CONFIG_NET_CLS_ACT) ? 6 : 1);
+
+#ifdef CONFIG_NET_CLS_ACT
+       *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);
+       *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);
+       *insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 2);
+       /* At ingress, value_reg = 0 */
+       *insn++ = BPF_MOV32_IMM(value_reg, 0);
+       *insn++ = BPF_JMP_A(1);
+#endif
+
+       /* value_reg = BPF_SKB_DELIVERYT_TIME_UNSPEC */
+       *insn++ = BPF_MOV32_IMM(value_reg, BPF_SKB_DELIVERY_TIME_UNSPEC);
+
+       /* 15 insns with CONFIG_NET_CLS_ACT */
+       return insn;
+}
+
 static struct bpf_insn *bpf_convert_shinfo_access(const struct bpf_insn *si,
                                                  struct bpf_insn *insn)
 {
@@ -8859,29 +8948,32 @@ static struct bpf_insn *bpf_convert_shinfo_access(const struct bpf_insn *si,
        return insn;
 }
 
-static struct bpf_insn *bpf_convert_tstamp_read(const struct bpf_insn *si,
+static struct bpf_insn *bpf_convert_tstamp_read(const struct bpf_prog *prog,
+                                               const struct bpf_insn *si,
                                                struct bpf_insn *insn)
 {
        __u8 value_reg = si->dst_reg;
        __u8 skb_reg = si->src_reg;
 
 #ifdef CONFIG_NET_CLS_ACT
-       __u8 tmp_reg = BPF_REG_AX;
-
-       *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);
-       *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);
-       *insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 5);
-       /* @ingress, read __sk_buff->tstamp as the (rcv) timestamp,
-        * so check the skb->mono_delivery_time.
-        */
-       *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
-                             SKB_MONO_DELIVERY_TIME_OFFSET);
-       *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
-                               SKB_MONO_DELIVERY_TIME_MASK);
-       *insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 2);
-       /* skb->mono_delivery_time is set, read 0 as the (rcv) timestamp. */
-       *insn++ = BPF_MOV64_IMM(value_reg, 0);
-       *insn++ = BPF_JMP_A(1);
+       if (!prog->delivery_time_access) {
+               __u8 tmp_reg = BPF_REG_AX;
+
+               *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);
+               *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);
+               *insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 5);
+               /* @ingress, read __sk_buff->tstamp as the (rcv) timestamp,
+                * so check the skb->mono_delivery_time.
+                */
+               *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
+                                     SKB_MONO_DELIVERY_TIME_OFFSET);
+               *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
+                                       SKB_MONO_DELIVERY_TIME_MASK);
+               *insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 2);
+               /* skb->mono_delivery_time is set, read 0 as the (rcv) timestamp. */
+               *insn++ = BPF_MOV64_IMM(value_reg, 0);
+               *insn++ = BPF_JMP_A(1);
+       }
 #endif
 
        *insn++ = BPF_LDX_MEM(BPF_DW, value_reg, skb_reg,
@@ -8889,27 +8981,30 @@ static struct bpf_insn *bpf_convert_tstamp_read(const struct bpf_insn *si,
        return insn;
 }
 
-static struct bpf_insn *bpf_convert_tstamp_write(const struct bpf_insn *si,
+static struct bpf_insn *bpf_convert_tstamp_write(const struct bpf_prog *prog,
+                                                const struct bpf_insn *si,
                                                 struct bpf_insn *insn)
 {
        __u8 value_reg = si->src_reg;
        __u8 skb_reg = si->dst_reg;
 
 #ifdef CONFIG_NET_CLS_ACT
-       __u8 tmp_reg = BPF_REG_AX;
-
-       *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);
-       *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);
-       *insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 3);
-       /* Writing __sk_buff->tstamp at ingress as the (rcv) timestamp.
-        * Clear the skb->mono_delivery_time.
-        */
-       *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
-                             SKB_MONO_DELIVERY_TIME_OFFSET);
-       *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
-                               ~SKB_MONO_DELIVERY_TIME_MASK);
-       *insn++ = BPF_STX_MEM(BPF_B, skb_reg, tmp_reg,
-                             SKB_MONO_DELIVERY_TIME_OFFSET);
+       if (!prog->delivery_time_access) {
+               __u8 tmp_reg = BPF_REG_AX;
+
+               *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg, TC_AT_INGRESS_OFFSET);
+               *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg, TC_AT_INGRESS_MASK);
+               *insn++ = BPF_JMP32_IMM(BPF_JEQ, tmp_reg, 0, 3);
+               /* Writing __sk_buff->tstamp at ingress as the (rcv) timestamp.
+                * Clear the skb->mono_delivery_time.
+                */
+               *insn++ = BPF_LDX_MEM(BPF_B, tmp_reg, skb_reg,
+                                     SKB_MONO_DELIVERY_TIME_OFFSET);
+               *insn++ = BPF_ALU32_IMM(BPF_AND, tmp_reg,
+                                       ~SKB_MONO_DELIVERY_TIME_MASK);
+               *insn++ = BPF_STX_MEM(BPF_B, skb_reg, tmp_reg,
+                                     SKB_MONO_DELIVERY_TIME_OFFSET);
+       }
 #endif
 
        /* skb->tstamp = tstamp */
@@ -9226,9 +9321,13 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type,
                BUILD_BUG_ON(sizeof_field(struct sk_buff, tstamp) != 8);
 
                if (type == BPF_WRITE)
-                       insn = bpf_convert_tstamp_write(si, insn);
+                       insn = bpf_convert_tstamp_write(prog, si, insn);
                else
-                       insn = bpf_convert_tstamp_read(si, insn);
+                       insn = bpf_convert_tstamp_read(prog, si, insn);
+               break;
+
+       case offsetof(struct __sk_buff, delivery_time_type):
+               insn = bpf_convert_dtime_type_read(si, insn);
                break;
 
        case offsetof(struct __sk_buff, gso_segs):

diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index afe3d0d..4eebea8 100644 (file)
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5086,6 +5086,37 @@ union bpf_attr {
  *     Return
  *             0 on success, or a negative error in case of failure. On error
  *             *dst* buffer is zeroed out.
+ *
+ * long bpf_skb_set_delivery_time(struct sk_buff *skb, u64 dtime, u32 dtime_type)
+ *     Description
+ *             Set a *dtime* (delivery time) to the __sk_buff->tstamp and also
+ *             change the __sk_buff->delivery_time_type to *dtime_type*.
+ *
+ *             When setting a delivery time (non zero *dtime*) to
+ *             __sk_buff->tstamp, only BPF_SKB_DELIVERY_TIME_MONO *dtime_type*
+ *             is supported.  It is the only delivery_time_type that will be
+ *             kept after bpf_redirect_*().
+ *
+ *             If there is no need to change the __sk_buff->delivery_time_type,
+ *             the delivery time can be directly written to __sk_buff->tstamp
+ *             instead.
+ *
+ *             *dtime* 0 and *dtime_type* BPF_SKB_DELIVERY_TIME_NONE
+ *             can be used to clear any delivery time stored in
+ *             __sk_buff->tstamp.
+ *
+ *             Only IPv4 and IPv6 skb->protocol are supported.
+ *
+ *             This function is most useful when it needs to set a
+ *             mono delivery time to __sk_buff->tstamp and then
+ *             bpf_redirect_*() to the egress of an iface.  For example,
+ *             changing the (rcv) timestamp in __sk_buff->tstamp at
+ *             ingress to a mono delivery time and then bpf_redirect_*()
+ *             to sch_fq@phy-dev.
+ *     Return
+ *             0 on success.
+ *             **-EINVAL** for invalid input
+ *             **-EOPNOTSUPP** for unsupported delivery_time_type and protocol
  */
 #define __BPF_FUNC_MAPPER(FN)          \
        FN(unspec),                     \
@@ -5280,6 +5311,7 @@ union bpf_attr {
        FN(xdp_load_bytes),             \
        FN(xdp_store_bytes),            \
        FN(copy_from_user_task),        \
+       FN(skb_set_delivery_time),      \
        /* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
@@ -5469,6 +5501,12 @@ union {                                  \
        __u64 :64;                      \
 } __attribute__((aligned(8)))
 
+enum {
+       BPF_SKB_DELIVERY_TIME_NONE,
+       BPF_SKB_DELIVERY_TIME_UNSPEC,
+       BPF_SKB_DELIVERY_TIME_MONO,
+};
+
 /* user accessible mirror of in-kernel sk_buff.
  * new fields can only be added to the end of this structure
  */
@@ -5509,7 +5547,8 @@ struct __sk_buff {
        __u32 gso_segs;
        __bpf_md_ptr(struct bpf_sock *, sk);
        __u32 gso_size;
-       __u32 :32;              /* Padding, future use. */
+       __u8  delivery_time_type;
+       __u32 :24;              /* Padding, future use. */
        __u64 hwtstamp;
 };