bpf: fix checksum in edge cases

hack3ric · Oct 1, 2024 · 39449c6 · 39449c6
1 parent 90ce2f3
commit 39449c6
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Showing 2 changed files with 6 additions and 6 deletions.
diff --git a/bpf/egress.c b/bpf/egress.c
@@ -28,16 +28,16 @@ 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 (max(data_len, reserve_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);
     }
   }
 
   if (padding_len > 0) {
     padding_len = min(padding_len, MAX_PADDING_LEN);
-    if (padding_len < 3) padding_len = 2;
-    if (padding_len < 2) padding_len = 1;
+    if (padding_len < 3)
+      if (padding_len < 2) padding_len = 1;
 
     for (int i = 0; i < padding_len / 4 + !!(padding_len % 4); i++)
       ((__u32*)buf)[i] = bpf_get_prandom_u32();

diff --git a/bpf/ingress.c b/bpf/ingress.c
@@ -20,8 +20,8 @@ static inline int restore_data(struct xdp_md* xdp, __u16 offset, __u32 buf_len,
 
   if (padding_len > 0) {
     padding_len = min(padding_len, MAX_PADDING_LEN);
-    if (padding_len < 3) padding_len = 2;
-    if (padding_len < 2) padding_len = 1;
+    if (padding_len < 3)
+      if (padding_len < 2) padding_len = 1;
 
     try_drop(bpf_xdp_load_bytes(xdp, offset, buf, padding_len));
     *csum_diff = bpf_csum_diff((__be32*)buf, round_to_mul(padding_len, 4), NULL, 0, *csum_diff);
@@ -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 (max(data_len, reserve_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);
     }