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clatd bpf - add try_make_readable() of the ethernet/ip header

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We now rely on the skb->mark = 0xDeadC1a7 setting side effect
for non offloadable packets, but for this to work reliably,
we *must* be able to read the ip header.

Test: TreeHugger, and on a gs101-based pixel
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ic2b15335099404047d136a92ce7aeeb1f11ccfa3
This commit is contained in:
Maciej Żenczykowski 2022-04-07 16:53:02 -07:00
commit 4b1e0f8bcf
1 changed files with 18 additions and 9 deletions
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27
bpf_progs/clatd.c
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@ -46,18 +46,24 @@
DEFINE_BPF_MAP_GRW(clat_ingress6_map, HASH, ClatIngress6Key, ClatIngress6Value, 16, AID_SYSTEM)
static inline __always_inline int nat64(struct __sk_buff* skb, bool is_ethernet) {
const int l2_header_size = is_ethernet ? sizeof(struct ethhdr) : 0;
void* data = (void*)(long)skb->data;
const void* data_end = (void*)(long)skb->data_end;
const struct ethhdr* const eth = is_ethernet ? data : NULL; // used iff is_ethernet
const struct ipv6hdr* const ip6 = is_ethernet ? (void*)(eth + 1) : data;
// Require ethernet dst mac address to be our unicast address.
if (is_ethernet && (skb->pkt_type != PACKET_HOST)) return TC_ACT_PIPE;
// Must be meta-ethernet IPv6 frame
if (skb->protocol != htons(ETH_P_IPV6)) return TC_ACT_PIPE;
const int l2_header_size = is_ethernet ? sizeof(struct ethhdr) : 0;
// Not clear if this is actually necessary considering we use DPA (Direct Packet Access),
// but we need to make sure we can read the IPv6 header reliably so that we can set
// skb->mark = 0xDeadC1a7 for packets we fail to offload.
try_make_readable(skb, l2_header_size + sizeof(struct ipv6hdr));
void* data = (void*)(long)skb->data;
const void* data_end = (void*)(long)skb->data_end;
const struct ethhdr* const eth = is_ethernet ? data : NULL; // used iff is_ethernet
const struct ipv6hdr* const ip6 = is_ethernet ? (void*)(eth + 1) : data;
// Must have (ethernet and) ipv6 header
if (data + l2_header_size + sizeof(*ip6) > data_end) return TC_ACT_PIPE;
@ -214,13 +220,16 @@ DEFINE_BPF_PROG("schedcls/egress4/clat_ether", AID_ROOT, AID_SYSTEM, sched_cls_e
DEFINE_BPF_PROG("schedcls/egress4/clat_rawip", AID_ROOT, AID_SYSTEM, sched_cls_egress4_clat_rawip)
(struct __sk_buff* skb) {
// Must be meta-ethernet IPv4 frame
if (skb->protocol != htons(ETH_P_IP)) return TC_ACT_PIPE;
// Possibly not needed, but for consistency with nat64 up above
try_make_readable(skb, sizeof(struct iphdr));
void* data = (void*)(long)skb->data;
const void* data_end = (void*)(long)skb->data_end;
const struct iphdr* const ip4 = data;
// Must be meta-ethernet IPv4 frame
if (skb->protocol != htons(ETH_P_IP)) return TC_ACT_PIPE;
// Must have ipv4 header
if (data + sizeof(*ip4) > data_end) return TC_ACT_PIPE;