Merge branch 'bpf-helper-improvements'

Daniel Borkmann says:

====================
BPF helper improvements

This set adds various BPF helper improvements, that is, cleaning
up and adding BPF_F_CURRENT_CPU flag for tracing helper, allowing
for preemption checks on bpf_get_smp_processor_id() helper, and
adding two new helpers bpf_skb_change_{proto, type} for tc related
programs. For further details please see individual patches.

Note, this set requires -net to be merged into -net-next tree first.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/bpf.h

@@ -313,6 +313,29 @@ enum bpf_func_id {
 	 */
 	BPF_FUNC_skb_get_tunnel_opt,
 	BPF_FUNC_skb_set_tunnel_opt,
+
+	/**
+	 * bpf_skb_change_proto(skb, proto, flags)
+	 * Change protocol of the skb. Currently supported is
+	 * v4 -> v6, v6 -> v4 transitions. The helper will also
+	 * resize the skb. eBPF program is expected to fill the
+	 * new headers via skb_store_bytes and lX_csum_replace.
+	 * @skb: pointer to skb
+	 * @proto: new skb->protocol type
+	 * @flags: reserved
+	 * Return: 0 on success or negative error
+	 */
+	BPF_FUNC_skb_change_proto,
+
+	/**
+	 * bpf_skb_change_type(skb, type)
+	 * Change packet type of skb.
+	 * @skb: pointer to skb
+	 * @type: new skb->pkt_type type
+	 * Return: 0 on success or negative error
+	 */
+	BPF_FUNC_skb_change_type,
+
 	__BPF_FUNC_MAX_ID,
 };
 
@@ -347,7 +370,7 @@ enum bpf_func_id {
 #define BPF_F_ZERO_CSUM_TX		(1ULL << 1)
 #define BPF_F_DONT_FRAGMENT		(1ULL << 2)
 
-/* BPF_FUNC_perf_event_output flags. */
+/* BPF_FUNC_perf_event_output and BPF_FUNC_perf_event_read flags. */
 #define BPF_F_INDEX_MASK		0xffffffffULL
 #define BPF_F_CURRENT_CPU		BPF_F_INDEX_MASK
 

kernel/bpf/core.c

@@ -719,14 +719,13 @@ select_insn:
 
 		if (unlikely(index >= array->map.max_entries))
 			goto out;
-
 		if (unlikely(tail_call_cnt > MAX_TAIL_CALL_CNT))
 			goto out;
 
 		tail_call_cnt++;
 
 		prog = READ_ONCE(array->ptrs[index]);
-		if (unlikely(!prog))
+		if (!prog)
 			goto out;
 
 		/* ARG1 at this point is guaranteed to point to CTX from

kernel/bpf/helpers.c

@@ -101,7 +101,7 @@ const struct bpf_func_proto bpf_get_prandom_u32_proto = {
 
 static u64 bpf_get_smp_processor_id(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
 {
-	return raw_smp_processor_id();
+	return smp_processor_id();
 }
 
 const struct bpf_func_proto bpf_get_smp_processor_id_proto = {

kernel/trace/bpf_trace.c

@@ -188,30 +188,35 @@ const struct bpf_func_proto *bpf_get_trace_printk_proto(void)
 	return &bpf_trace_printk_proto;
 }
 
-static u64 bpf_perf_event_read(u64 r1, u64 index, u64 r3, u64 r4, u64 r5)
+static u64 bpf_perf_event_read(u64 r1, u64 flags, u64 r3, u64 r4, u64 r5)
 {
 	struct bpf_map *map = (struct bpf_map *) (unsigned long) r1;
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
+	unsigned int cpu = smp_processor_id();
+	u64 index = flags & BPF_F_INDEX_MASK;
 	struct bpf_event_entry *ee;
 	struct perf_event *event;
 
+	if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
+		return -EINVAL;
+	if (index == BPF_F_CURRENT_CPU)
+		index = cpu;
 	if (unlikely(index >= array->map.max_entries))
 		return -E2BIG;
 
 	ee = READ_ONCE(array->ptrs[index]);
-	if (unlikely(!ee))
+	if (!ee)
 		return -ENOENT;
 
 	event = ee->event;
-	/* make sure event is local and doesn't have pmu::count */
-	if (event->oncpu != smp_processor_id() ||
-	    event->pmu->count)
-		return -EINVAL;
-
 	if (unlikely(event->attr.type != PERF_TYPE_HARDWARE &&
 		     event->attr.type != PERF_TYPE_RAW))
 		return -EINVAL;
 
+	/* make sure event is local and doesn't have pmu::count */
+	if (unlikely(event->oncpu != cpu || event->pmu->count))
+		return -EINVAL;
+
 	/*
 	 * we don't know if the function is run successfully by the
 	 * return value. It can be judged in other places, such as
@@ -233,6 +238,7 @@ static u64 bpf_perf_event_output(u64 r1, u64 r2, u64 flags, u64 r4, u64 size)
 	struct pt_regs *regs = (struct pt_regs *) (long) r1;
 	struct bpf_map *map = (struct bpf_map *) (long) r2;
 	struct bpf_array *array = container_of(map, struct bpf_array, map);
+	unsigned int cpu = smp_processor_id();
 	u64 index = flags & BPF_F_INDEX_MASK;
 	void *data = (void *) (long) r4;
 	struct perf_sample_data sample_data;
@@ -246,12 +252,12 @@ static u64 bpf_perf_event_output(u64 r1, u64 r2, u64 flags, u64 r4, u64 size)
 	if (unlikely(flags & ~(BPF_F_INDEX_MASK)))
 		return -EINVAL;
 	if (index == BPF_F_CURRENT_CPU)
-		index = raw_smp_processor_id();
+		index = cpu;
 	if (unlikely(index >= array->map.max_entries))
 		return -E2BIG;
 
 	ee = READ_ONCE(array->ptrs[index]);
-	if (unlikely(!ee))
+	if (!ee)
 		return -ENOENT;
 
 	event = ee->event;
@@ -259,7 +265,7 @@ static u64 bpf_perf_event_output(u64 r1, u64 r2, u64 flags, u64 r4, u64 size)
 		     event->attr.config != PERF_COUNT_SW_BPF_OUTPUT))
 		return -EINVAL;
 
-	if (unlikely(event->oncpu != smp_processor_id()))
+	if (unlikely(event->oncpu != cpu))
 		return -EOPNOTSUPP;
 
 	perf_sample_data_init(&sample_data, 0, 0);
@@ -354,18 +360,12 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func
 static bool kprobe_prog_is_valid_access(int off, int size, enum bpf_access_type type,
 					enum bpf_reg_type *reg_type)
 {
-	/* check bounds */
 	if (off < 0 || off >= sizeof(struct pt_regs))
 		return false;
-
-	/* only read is allowed */
 	if (type != BPF_READ)
 		return false;
-
-	/* disallow misaligned access */
 	if (off % size != 0)
 		return false;
-
 	return true;
 }
 

net/core/filter.c

@@ -150,6 +150,12 @@ static u64 __get_raw_cpu_id(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)
 	return raw_smp_processor_id();
 }
 
+static const struct bpf_func_proto bpf_get_raw_smp_processor_id_proto = {
+	.func		= __get_raw_cpu_id,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+};
+
 static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg,
 			      struct bpf_insn *insn_buf)
 {
@@ -1777,6 +1783,224 @@ const struct bpf_func_proto bpf_skb_vlan_pop_proto = {
 };
 EXPORT_SYMBOL_GPL(bpf_skb_vlan_pop_proto);
 
+static int 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.
+	 */
+	skb_push(skb, len);
+	memmove(skb->data, skb->data + len, off);
+	memset(skb->data + off, 0, len);
+
+	/* No skb_postpush_rcsum(skb, skb->data + off, len)
+	 * needed here as it does not change the skb->csum
+	 * 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)
+{
+	/* skb_ensure_writable() is not needed here, as we're
+	 * already working on an uncloned skb.
+	 */
+	if (unlikely(!pskb_may_pull(skb, off + len)))
+		return -ENOMEM;
+
+	skb_postpull_rcsum(skb, skb->data + off, len);
+	memmove(skb->data + len, skb->data, off);
+	__skb_pull(skb, len);
+
+	return 0;
+}
+
+static int 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;
+}
+
+static int bpf_skb_net_hdr_pop(struct sk_buff *skb, u32 off, u32 len)
+{
+	bool trans_same = skb->transport_header == skb->network_header;
+	int ret;
+
+	/* Same here, __skb_push()/__skb_pull() pair not needed. */
+	ret = bpf_skb_generic_pop(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;
+}
+
+static int bpf_skb_proto_4_to_6(struct sk_buff *skb)
+{
+	const u32 len_diff = sizeof(struct ipv6hdr) - sizeof(struct iphdr);
+	u32 off = skb->network_header - skb->mac_header;
+	int ret;
+
+	ret = skb_cow(skb, len_diff);
+	if (unlikely(ret < 0))
+		return ret;
+
+	ret = bpf_skb_net_hdr_push(skb, off, len_diff);
+	if (unlikely(ret < 0))
+		return ret;
+
+	if (skb_is_gso(skb)) {
+		/* SKB_GSO_UDP stays as is. SKB_GSO_TCPV4 needs to
+		 * be changed into SKB_GSO_TCPV6.
+		 */
+		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4) {
+			skb_shinfo(skb)->gso_type &= ~SKB_GSO_TCPV4;
+			skb_shinfo(skb)->gso_type |=  SKB_GSO_TCPV6;
+		}
+
+		/* Due to IPv6 header, MSS needs to be downgraded. */
+		skb_shinfo(skb)->gso_size -= len_diff;
+		/* Header must be checked, and gso_segs recomputed. */
+		skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
+		skb_shinfo(skb)->gso_segs = 0;
+	}
+
+	skb->protocol = htons(ETH_P_IPV6);
+	skb_clear_hash(skb);
+
+	return 0;
+}
+
+static int bpf_skb_proto_6_to_4(struct sk_buff *skb)
+{
+	const u32 len_diff = sizeof(struct ipv6hdr) - sizeof(struct iphdr);
+	u32 off = skb->network_header - skb->mac_header;
+	int ret;
+
+	ret = skb_unclone(skb, GFP_ATOMIC);
+	if (unlikely(ret < 0))
+		return ret;
+
+	ret = bpf_skb_net_hdr_pop(skb, off, len_diff);
+	if (unlikely(ret < 0))
+		return ret;
+
+	if (skb_is_gso(skb)) {
+		/* SKB_GSO_UDP stays as is. SKB_GSO_TCPV6 needs to
+		 * be changed into SKB_GSO_TCPV4.
+		 */
+		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6) {
+			skb_shinfo(skb)->gso_type &= ~SKB_GSO_TCPV6;
+			skb_shinfo(skb)->gso_type |=  SKB_GSO_TCPV4;
+		}
+
+		/* Due to IPv4 header, MSS can be upgraded. */
+		skb_shinfo(skb)->gso_size += len_diff;
+		/* Header must be checked, and gso_segs recomputed. */
+		skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
+		skb_shinfo(skb)->gso_segs = 0;
+	}
+
+	skb->protocol = htons(ETH_P_IP);
+	skb_clear_hash(skb);
+
+	return 0;
+}
+
+static int bpf_skb_proto_xlat(struct sk_buff *skb, __be16 to_proto)
+{
+	__be16 from_proto = skb->protocol;
+
+	if (from_proto == htons(ETH_P_IP) &&
+	      to_proto == htons(ETH_P_IPV6))
+		return bpf_skb_proto_4_to_6(skb);
+
+	if (from_proto == htons(ETH_P_IPV6) &&
+	      to_proto == htons(ETH_P_IP))
+		return bpf_skb_proto_6_to_4(skb);
+
+	return -ENOTSUPP;
+}
+
+static u64 bpf_skb_change_proto(u64 r1, u64 r2, u64 flags, u64 r4, u64 r5)
+{
+	struct sk_buff *skb = (struct sk_buff *) (long) r1;
+	__be16 proto = (__force __be16) r2;
+	int ret;
+
+	if (unlikely(flags))
+		return -EINVAL;
+
+	/* General idea is that this helper does the basic groundwork
+	 * needed for changing the protocol, and eBPF program fills the
+	 * rest through bpf_skb_store_bytes(), bpf_lX_csum_replace()
+	 * and other helpers, rather than passing a raw buffer here.
+	 *
+	 * The rationale is to keep this minimal and without a need to
+	 * deal with raw packet data. F.e. even if we would pass buffers
+	 * here, the program still needs to call the bpf_lX_csum_replace()
+	 * helpers anyway. Plus, this way we keep also separation of
+	 * concerns, since f.e. bpf_skb_store_bytes() should only take
+	 * care of stores.
+	 *
+	 * Currently, additional options and extension header space are
+	 * not supported, but flags register is reserved so we can adapt
+	 * that. For offloads, we mark packet as dodgy, so that headers
+	 * need to be verified first.
+	 */
+	ret = bpf_skb_proto_xlat(skb, proto);
+	bpf_compute_data_end(skb);
+	return ret;
+}
+
+static const struct bpf_func_proto bpf_skb_change_proto_proto = {
+	.func		= bpf_skb_change_proto,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_ANYTHING,
+	.arg3_type	= ARG_ANYTHING,
+};
+
+static u64 bpf_skb_change_type(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{
+	struct sk_buff *skb = (struct sk_buff *) (long) r1;
+	u32 pkt_type = r2;
+
+	/* We only allow a restricted subset to be changed for now. */
+	if (unlikely(skb->pkt_type > PACKET_OTHERHOST ||
+		     pkt_type > PACKET_OTHERHOST))
+		return -EINVAL;
+
+	skb->pkt_type = pkt_type;
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_skb_change_type_proto = {
+	.func		= bpf_skb_change_type,
+	.gpl_only	= false,
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_CTX,
+	.arg2_type	= ARG_ANYTHING,
+};
+
 bool bpf_helper_changes_skb_data(void *func)
 {
 	if (func == bpf_skb_vlan_push)
@@ -1785,6 +2009,8 @@ bool bpf_helper_changes_skb_data(void *func)
 		return true;
 	if (func == bpf_skb_store_bytes)
 		return true;
+	if (func == bpf_skb_change_proto)
+		return true;
 	if (func == bpf_l3_csum_replace)
 		return true;
 	if (func == bpf_l4_csum_replace)
@@ -2037,7 +2263,7 @@ sk_filter_func_proto(enum bpf_func_id func_id)
 	case BPF_FUNC_get_prandom_u32:
 		return &bpf_get_prandom_u32_proto;
 	case BPF_FUNC_get_smp_processor_id:
-		return &bpf_get_smp_processor_id_proto;
+		return &bpf_get_raw_smp_processor_id_proto;
 	case BPF_FUNC_tail_call:
 		return &bpf_tail_call_proto;
 	case BPF_FUNC_ktime_get_ns:
@@ -2072,6 +2298,10 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
 		return &bpf_skb_vlan_push_proto;
 	case BPF_FUNC_skb_vlan_pop:
 		return &bpf_skb_vlan_pop_proto;
+	case BPF_FUNC_skb_change_proto:
+		return &bpf_skb_change_proto_proto;
+	case BPF_FUNC_skb_change_type:
+		return &bpf_skb_change_type_proto;
 	case BPF_FUNC_skb_get_tunnel_key:
 		return &bpf_skb_get_tunnel_key_proto;
 	case BPF_FUNC_skb_set_tunnel_key:
@@ -2086,6 +2316,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
 		return &bpf_get_route_realm_proto;
 	case BPF_FUNC_perf_event_output:
 		return bpf_get_event_output_proto();
+	case BPF_FUNC_get_smp_processor_id:
+		return &bpf_get_smp_processor_id_proto;
 	default:
 		return sk_filter_func_proto(func_id);
 	}