dhcp: use iov_tail rather than pool

This patch refactors the dhcp() function to accept `struct iov_tail *data`
directly as its packet input, replacing the previous `const struct pool *p`
parameter. Consequently, dhcp() no longer fetches packet data internally
using packet_data().

This change simplifies callers, such as tap4_handler(), which now pass
the iov_tail representing the L2 frame directly to dhcp(). This removes
the need for intermediate packet pool handling for DHCP processing.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

3 files changed, 16 insertions, 23 deletions

diff --git a/dhcp.c b/dhcp.c
index 8117529..012cec6 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -296,11 +296,11 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len)
 /**
  * dhcp() - Check if this is a DHCP message, reply as needed
  * @c:		Execution context
- * @p:		Packet pool, single packet with Ethernet buffer
+ * @data:	Single packet with Ethernet buffer
  *
  * Return: 0 if it's not a DHCP message, 1 if handled, -1 on failure
  */
-int dhcp(const struct ctx *c, const struct pool *p)
+int dhcp(const struct ctx *c, struct iov_tail *data)
 {
 	char macstr[ETH_ADDRSTRLEN];
 	size_t mlen, dlen, opt_len;
@@ -311,24 +311,20 @@ int dhcp(const struct ctx *c, const struct pool *p)
 	const struct ethhdr *eh;
 	const struct iphdr *iph;
 	const struct udphdr *uh;
-	struct iov_tail data;
 	struct msg const *m;
 	struct msg reply;
 	unsigned int i;
 	struct msg m_storage;
 
-	if (!packet_get(p, 0, &data))
-		return -1;
-
-	eh = IOV_REMOVE_HEADER(&data, eh_storage);
-	iph = IOV_PEEK_HEADER(&data, iph_storage);
+	eh = IOV_REMOVE_HEADER(data, eh_storage);
+	iph = IOV_PEEK_HEADER(data, iph_storage);
 	if (!eh || !iph)
 		return -1;
 
-	if (!iov_drop_header(&data, iph->ihl * 4UL))
+	if (!iov_drop_header(data, iph->ihl * 4UL))
 		return -1;
 
-	uh = IOV_REMOVE_HEADER(&data, uh_storage);
+	uh = IOV_REMOVE_HEADER(data, uh_storage);
 	if (!uh)
 		return -1;
 
@@ -338,8 +334,8 @@ int dhcp(const struct ctx *c, const struct pool *p)
 	if (c->no_dhcp)
 		return 1;
 
-	mlen = iov_tail_size(&data);
-	m = (struct msg const *)iov_remove_header_(&data, &m_storage,
+	mlen = iov_tail_size(data);
+	m = (struct msg const *)iov_remove_header_(data, &m_storage,
 						   offsetof(struct msg, o),
 						   __alignof__(struct msg));
 	if (!m						||
@@ -367,24 +363,24 @@ int dhcp(const struct ctx *c, const struct pool *p)
 	for (i = 0; i < ARRAY_SIZE(opts); i++)
 		opts[i].clen = -1;
 
-	opt_len = iov_tail_size(&data);
+	opt_len = iov_tail_size(data);
 	while (opt_len >= 2) {
 		uint8_t olen_storage, type_storage;
 		const uint8_t *olen;
 		uint8_t *type;
 
-		type = IOV_REMOVE_HEADER(&data, type_storage);
-		olen = IOV_REMOVE_HEADER(&data, olen_storage);
+		type = IOV_REMOVE_HEADER(data, type_storage);
+		olen = IOV_REMOVE_HEADER(data, olen_storage);
 		if (!type || !olen)
 			return -1;
 
-		opt_len = iov_tail_size(&data);
+		opt_len = iov_tail_size(data);
 		if (opt_len < *olen)
 			return -1;
 
-		iov_to_buf(&data.iov[0], data.cnt, data.off, &opts[*type].c, *olen);
+		iov_to_buf(&data->iov[0], data->cnt, data->off, &opts[*type].c, *olen);
 		opts[*type].clen = *olen;
-		iov_drop_header(&data, *olen);
+		iov_drop_header(data, *olen);
 		opt_len -= *olen;
 	}
 
diff --git a/dhcp.h b/dhcp.h
index 87aeecd..cd50c99 100644
--- a/dhcp.h
+++ b/dhcp.h
@@ -6,7 +6,7 @@
 #ifndef DHCP_H
 #define DHCP_H
 
-int dhcp(const struct ctx *c, const struct pool *p);
+int dhcp(const struct ctx *c, struct iov_tail *data);
 void dhcp_init(void);
 
 #endif /* DHCP_H */
diff --git a/tap.c b/tap.c
index 7a538b2..14050b3 100644
--- a/tap.c
+++ b/tap.c
@@ -785,11 +785,8 @@ resume:
 		if (iph->protocol == IPPROTO_UDP) {
 			struct iov_tail eh_data;
 
-			PACKET_POOL_P(pkt, 1, in->buf, in->buf_size);
-
 			packet_get(in, i, &eh_data);
-			packet_add(pkt, &eh_data);
-			if (dhcp(c, pkt))
+			if (dhcp(c, &eh_data))
 				continue;
 		}