This patch adds all needed plumbing in preparation to allowing
bpf programs to do IP encapping via bpf_lwt_push_encap. Actual
implementation is added in the next patch in the patchset.
Of note:
- bpf_lwt_push_encap can now be called from BPF_PROG_TYPE_LWT_XMIT
prog types in addition to BPF_PROG_TYPE_LWT_IN;
- as route lookups are different for ingress vs egress, the single
external bpf_lwt_push_encap BPF helper is routed internally to
either bpf_lwt_in_push_encap or bpf_lwt_xmit_push_encap BPF_CALLs,
depending on prog type.
Signed-off-by: Peter Oskolkov <p...@google.com>
---
include/uapi/linux/bpf.h | 23 ++++++++++++++++++--
net/core/filter.c | 46 +++++++++++++++++++++++++++++++++++-----
2 files changed, 62 insertions(+), 7 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 60b99b730a41..911c15585fab 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -2015,6 +2015,16 @@ union bpf_attr {
* Only works if *skb* contains an IPv6 packet. Insert a
* Segment Routing Header (**struct ipv6_sr_hdr**) inside
* the IPv6 header.
+ * **BPF_LWT_ENCAP_IP**
+ * IP encapsulation (GRE/GUE/IPIP/etc). The outer header
+ * must be IPv4 or IPv6, followed by zero or more
+ * additional headers, up to LWT_BPF_MAX_HEADROOM total
+ * bytes in all prepended headers.
+ *
+ * BPF_LWT_ENCAP_SEG6*** types can be called by bpf programs of
+ * type BPF_PROG_TYPE_LWT_IN; BPF_LWT_ENCAP_IP type can be called
+ * by bpf programs of types BPF_PROG_TYPE_LWT_IN and
+ * BPF_PROG_TYPE_LWT_XMIT.
*
* A call to this helper is susceptible to change the underlaying
* packet buffer. Therefore, at load time, all checks on pointers
@@ -2495,7 +2505,8 @@ enum bpf_hdr_start_off {
/* Encapsulation type for BPF_FUNC_lwt_push_encap helper. */
enum bpf_lwt_encap_mode {
BPF_LWT_ENCAP_SEG6,
- BPF_LWT_ENCAP_SEG6_INLINE
+ BPF_LWT_ENCAP_SEG6_INLINE,
+ BPF_LWT_ENCAP_IP,
};
#define __bpf_md_ptr(type, name) \
@@ -2583,7 +2594,15 @@ enum bpf_ret_code {
BPF_DROP = 2,
/* 3-6 reserved */
BPF_REDIRECT = 7,
- /* >127 are reserved for prog type specific return codes */
+ /* >127 are reserved for prog type specific return codes.
+ *
+ * BPF_LWT_REROUTE: used by BPF_PROG_TYPE_LWT_IN and
+ * BPF_PROG_TYPE_LWT_XMIT to indicate that skb had been
+ * changed and should be routed based on its new L3 header.
+ * (This is an L3 redirect, as opposed to L2 redirect
+ * represented by BPF_REDIRECT above).
+ */
+ BPF_LWT_REROUTE = 128,
};
struct bpf_sock {
diff --git a/net/core/filter.c b/net/core/filter.c
index 41984ad4b9b4..27d3fbe4b77b 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4801,7 +4801,13 @@ static int bpf_push_seg6_encap(struct sk_buff *skb, u32
type, void *hdr, u32 len
}
#endif /* CONFIG_IPV6_SEG6_BPF */
-BPF_CALL_4(bpf_lwt_push_encap, struct sk_buff *, skb, u32, type, void *, hdr,
+static int bpf_push_ip_encap(struct sk_buff *skb, void *hdr, u32 len,
+ bool ingress)
+{
+ return -EINVAL; /* Implemented in the next patch. */
+}
+
+BPF_CALL_4(bpf_lwt_in_push_encap, struct sk_buff *, skb, u32, type, void *,
hdr,
u32, len)
{
switch (type) {
@@ -4809,14 +4815,41 @@ BPF_CALL_4(bpf_lwt_push_encap, struct sk_buff *, skb,
u32, type, void *, hdr,
case BPF_LWT_ENCAP_SEG6:
case BPF_LWT_ENCAP_SEG6_INLINE:
return bpf_push_seg6_encap(skb, type, hdr, len);
+#endif
+#if IS_ENABLED(CONFIG_LWTUNNEL_BPF)
+ case BPF_LWT_ENCAP_IP:
+ return bpf_push_ip_encap(skb, hdr, len, true /* ingress */);
#endif
default:
return -EINVAL;
}
}
-static const struct bpf_func_proto bpf_lwt_push_encap_proto = {
- .func = bpf_lwt_push_encap,
+BPF_CALL_4(bpf_lwt_xmit_push_encap, struct sk_buff *, skb, u32, type,
+ void *, hdr, u32, len)
+{
+ switch (type) {
+#if IS_ENABLED(CONFIG_LWTUNNEL_BPF)
+ case BPF_LWT_ENCAP_IP:
+ return bpf_push_ip_encap(skb, hdr, len, false /* egress */);
+#endif
+ default:
+ return -EINVAL;
+ }
+}
+
+static const struct bpf_func_proto bpf_lwt_in_push_encap_proto = {
+ .func = bpf_lwt_in_push_encap,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+ .arg2_type = ARG_ANYTHING,
+ .arg3_type = ARG_PTR_TO_MEM,
+ .arg4_type = ARG_CONST_SIZE
+};
+
+static const struct bpf_func_proto bpf_lwt_xmit_push_encap_proto = {
+ .func = bpf_lwt_xmit_push_encap,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
@@ -5282,7 +5315,8 @@ bool bpf_helper_changes_pkt_data(void *func)
func == bpf_lwt_seg6_adjust_srh ||
func == bpf_lwt_seg6_action ||
#endif
- func == bpf_lwt_push_encap)
+ func == bpf_lwt_in_push_encap ||
+ func == bpf_lwt_xmit_push_encap)
return true;
return false;
@@ -5660,7 +5694,7 @@ lwt_in_func_proto(enum bpf_func_id func_id, const struct
bpf_prog *prog)
{
switch (func_id) {
case BPF_FUNC_lwt_push_encap:
- return &bpf_lwt_push_encap_proto;
+ return &bpf_lwt_in_push_encap_proto;
default:
return lwt_out_func_proto(func_id, prog);
}
@@ -5696,6 +5730,8 @@ lwt_xmit_func_proto(enum bpf_func_id func_id, const
struct bpf_prog *prog)
return &bpf_l4_csum_replace_proto;
case BPF_FUNC_set_hash_invalid:
return &bpf_set_hash_invalid_proto;
+ case BPF_FUNC_lwt_push_encap:
+ return &bpf_lwt_xmit_push_encap_proto;
default:
return lwt_out_func_proto(func_id, prog);
}
--
2.20.1.611.gfbb209baf1-goog
