diff options
| -rw-r--r-- | include/uapi/linux/bpf.h | 14 | ||||
| -rw-r--r-- | net/core/filter.c | 200 |
2 files changed, 214 insertions, 0 deletions
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 58df2da3e9bf..66cd738a937a 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -313,6 +313,20 @@ 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_FUNC_MAX_ID, }; diff --git a/net/core/filter.c b/net/core/filter.c index 46c88d9cec5c..d983e765787a 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -1783,6 +1783,202 @@ 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, +}; + bool bpf_helper_changes_skb_data(void *func) { if (func == bpf_skb_vlan_push) @@ -1791,6 +1987,8 @@ 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) @@ -2078,6 +2276,8 @@ 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_get_tunnel_key: return &bpf_skb_get_tunnel_key_proto; case BPF_FUNC_skb_set_tunnel_key: |