bpf: fix checksum in edge cases

hack3ric · Oct 1, 2024 · 99b9723 · 99b9723
1 parent 90ce2f3
commit 99b9723
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Showing 2 changed files with 2 additions and 2 deletions.
diff --git a/bpf/egress.c b/bpf/egress.c
@@ -28,7 +28,7 @@ static inline int mangle_data(struct __sk_buff* skb, __u16 offset, __be32* csum_
     try_shot(bpf_skb_store_bytes(skb, skb->len - copy_len, buf + 1, copy_len, 0));
 
     // Fix checksum when moved bytes does not align with u16 boundaries
-    if (copy_len == reserve_len && data_len % 2 != 0) {
+    if ((data_len <= copy_len && reserve_len % 2 != 0) || data_len % 2 != 0) {
       __u32 l = min(round_to_mul(copy_len, 4), MAX_RESERVE_LEN);
       *csum_diff = bpf_csum_diff((__be32*)(buf + 1), l, (__be32*)buf, l + 4, *csum_diff);
     }

diff --git a/bpf/ingress.c b/bpf/ingress.c
@@ -36,7 +36,7 @@ static inline int restore_data(struct xdp_md* xdp, __u16 offset, __u32 buf_len,
     try_drop(bpf_xdp_store_bytes(xdp, offset - TCP_UDP_HEADER_DIFF, buf + 1, copy_len));
 
     // Fix checksum when moved bytes does not align with u16 boundaries
-    if (copy_len == reserve_len && data_len % 2 != 0) {
+    if ((data_len <= copy_len && copy_len % 2 != 0) || data_len % 2 != 0) {
       __u32 l = min(round_to_mul(copy_len, 4), MAX_RESERVE_LEN);
       *csum_diff = bpf_csum_diff((__be32*)buf, l + 4, (__be32*)(buf + 1), l, *csum_diff);
     }