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bpf/progs/netd.c: 5.4+ uses skb->gso_segs > 1 instead of skb->len > 1500

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add a minor comment to clarify tcphdr and udphdr size.

rename is_tcp to is_tcp_or_unknown to make the code more explicit.

Bug: 263884894
Test: TreeHugger
Flag: EXEMPT mainline
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: Ie3417299564bc712c2e78fc6665c979e48d3013b
This commit is contained in:
Maciej Żenczykowski 2025-07-03 09:33:52 -07:00
commit 204ee23112
1 changed files with 6 additions and 4 deletions
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10
bpf/progs/netd.c
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@ -183,16 +183,18 @@ DEFINE_BPF_MAP_EXT(local_net_blocked_uid_map, HASH, uint32_t, bool, -1000,
value = bpf_##the_stats_map##_lookup_elem(key); \
} \
if (value) { \
const bool is5_4 = KVER_IS_AT_LEAST(kver, 5, 4, 0); \
const int mtu = 1500; \
uint64_t packets = 1; \
uint64_t bytes = skb->len; \
if (bytes > mtu) { \
const bool is5_4 = KVER_IS_AT_LEAST(kver, 5, 4, 0); \
if ((!is5_4 && bytes > mtu) || (is5_4 && skb->gso_segs > 1)) { \
const bool is_ipv6 = (skb->protocol == htons(ETH_P_IPV6)); \
const int ip_overhead = is_ipv6 ? sizeof(struct ipv6hdr) : sizeof(struct iphdr); \
struct bpf_sock * const sk = is5_4 && skb->sk ? bpf_sk_fullsock(skb->sk) : NULL; \
const bool is_tcp = !sk || sk->protocol == IPPROTO_TCP; \
const int L4_size = is_tcp ? sizeof(struct tcphdr) + 12 : sizeof(struct udphdr); \
const bool is_tcp_or_unknown = !sk || sk->protocol == IPPROTO_TCP; \
const int tcphdr_size = sizeof(struct tcphdr); \
const int udphdr_size = sizeof(struct udphdr); \
const int L4_size = is_tcp_or_unknown ? tcphdr_size + 12 : udphdr_size; \
const int overhead = ip_overhead + L4_size; \
const int mss = mtu - overhead; \
const uint64_t payload = bytes - overhead; \