Re: [PATCH v8 20/30] tap: Convert tap6_handler() to iov_tail

6 Aug 2025


      On Tue, Aug 05, 2025 at 05:46:18PM +0200, Laurent Vivier wrote:
...
Use packet_data() and extract headers using IOV_REMOVE_HEADER()
and IOV_PEEK_HEADER() rather than packet_get().
Remove packet_get() as it is not used anymore.
[snip]
...
@@ -896,21 +896,28 @@ resume:
  for (seq_count = 0, seq = NULL; i < in->count; i++) {
      size_t l4len, plen, check;
      struct in6_addr *saddr, *daddr;
+		struct ipv6hdr ip6h_storage;
+		struct ethhdr eh_storage;
+		struct udphdr uh_storage;
      const struct ethhdr *eh;
      const struct udphdr *uh;
      struct iov_tail data;
      struct ipv6hdr *ip6h;
      uint8_t proto;
-		char *l4h;
-		eh =   packet_get(in, i, 0,		sizeof(*eh), NULL);
+		if (!packet_data(in, i, &data))
+			return -1;
+
+		eh = IOV_REMOVE_HEADER(&data, eh_storage);
      if (!eh)
      	continue;
-		ip6h = packet_get(in, i, sizeof(*eh),	sizeof(*ip6h), &check);
+		ip6h = IOV_PEEK_HEADER(&data, ip6h_storage);
      if (!ip6h)
      	continue;
You peek the IPv6 header here, but I haven't spotted where you remove
/ drop it before...
...
+		check = iov_tail_size(&data) - sizeof(*ip6h);
+
      saddr = &ip6h->saddr;
      daddr = &ip6h->daddr;
@@ -918,10 +925,8 @@ resume:
      if (plen != check)
      	continue;
-		data = IOV_TAIL_FROM_BUF(ip6h, sizeof(*ip6h) + check, 0);
      if (!ipv6_l4hdr(&data, &proto, &l4len))
      	continue;
-		l4h = (char *)data.iov[0].iov_base + data.off;
if (IN6_IS_ADDR_LOOPBACK(saddr) || IN6_IS_ADDR_LOOPBACK(daddr)) {
      	char sstr[INET6_ADDRSTRLEN], dstr[INET6_ADDRSTRLEN];
@@ -946,6 +951,8 @@ resume:
      }
if (proto == IPPROTO_ICMPV6) {
+			struct icmp6hdr l4h_storage;
+			const struct icmp6hdr *l4h;
      	PACKET_POOL_P(pkt, 1, in->buf, in->buf_size);
if (c->no_icmp)
@@ -954,9 +961,9 @@ resume:
      	if (l4len < sizeof(struct icmp6hdr))
      		continue;
-			data = IOV_TAIL_FROM_BUF(l4h, l4len, 0);
      	packet_add(pkt, &data);
+			l4h = IOV_PEEK_HEADER(&data, l4h_storage);
... peeking the next header here.
...
if (ndp(c, (struct icmp6hdr *)l4h, saddr, pkt))
      		continue;
@@ -969,12 +976,13 @@ resume:
if (l4len < sizeof(*uh))
      	continue;
-		uh = (struct udphdr *)l4h;
+		uh = IOV_PEEK_HEADER(&data, uh_storage);
And here.
...
+		if (!uh)
+			continue;
if (proto == IPPROTO_UDP) {
      	PACKET_POOL_P(pkt, 1, in->buf, in->buf_size);
-			data = IOV_TAIL_FROM_BUF(l4h, l4len, 0);
      	packet_add(pkt, &data);
if (dhcpv6(c, pkt, saddr, daddr))
@@ -1031,7 +1039,6 @@ resume:
 #undef L4_SET
append:
-		data = IOV_TAIL_FROM_BUF(l4h, l4len, 0);
      packet_add((struct pool *)&seq->p, &data);
  }
-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

    