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From: Jon Maloy <jmaloy@redhat.com>
To: passt-dev@passt.top,
sbrivio@redhat.com,
lvivier@redhat.com,
dgibson@redhat.com,
jmaloy@redhat.com
Subject: [PATCH v5 1/4] tap: break out building of udp header from tap_udp4_send function
Date: Sun, 23 Feb 2025 17:59:48 -0500
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We will need to build the UDP header at other locations than in function
tap_udp4_send(), so we break that part out to a separate function.
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
tap.c | 32 +++++++++++++++++++++++++-------
tap.h | 5 +++++
2 files changed, 30 insertions(+), 7 deletions(-)
diff --git a/tap.c b/tap.c
index 44b0fc0..932eef6 100644
--- a/tap.c
+++ b/tap.c
@@ -163,7 +163,7 @@ static void *tap_push_ip4h(struct iphdr *ip4h, struct in_addr src,
}
/**
- * tap_udp4_send() - Send UDP over IPv4 packet
+ * tap_push_uh4() - Build UDPv4 header with checksum
* @c: Execution context
* @src: IPv4 source address
* @sport: UDP source port
@@ -172,15 +172,11 @@ static void *tap_push_ip4h(struct iphdr *ip4h, struct in_addr src,
* @in: UDP payload contents (not including UDP header)
* @dlen: UDP payload length (not including UDP header)
*/
-void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
+void *tap_push_uh4(struct udphdr *uh, struct in_addr src, in_port_t sport,
struct in_addr dst, in_port_t dport,
const void *in, size_t dlen)
{
size_t l4len = dlen + sizeof(struct udphdr);
- char buf[USHRT_MAX];
- struct iphdr *ip4h = tap_push_l2h(c, buf, ETH_P_IP);
- struct udphdr *uh = tap_push_ip4h(ip4h, src, dst, l4len, IPPROTO_UDP);
- char *data = (char *)(uh + 1);
const struct iovec iov = {
.iov_base = (void *)in,
.iov_len = dlen
@@ -191,8 +187,30 @@ void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
uh->dest = htons(dport);
uh->len = htons(l4len);
csum_udp4(uh, src, dst, &payload);
- memcpy(data, in, dlen);
+ return uh + 1;
+}
+
+/**
+ * tap_udp4_send() - Send UDP over IPv4 packet
+ * @c: Execution context
+ * @src: IPv4 source address
+ * @sport: UDP source port
+ * @dst: IPv4 destination address
+ * @dport: UDP destination port
+ * @in: UDP payload contents (not including UDP header)
+ * @dlen: UDP payload length (not including UDP header)
+ */
+void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
+ struct in_addr dst, in_port_t dport,
+ const void *in, size_t dlen)
+{
+ size_t l4len = dlen + sizeof(struct udphdr);
+ char buf[USHRT_MAX];
+ struct iphdr *ip4h = tap_push_l2h(c, buf, ETH_P_IP);
+ struct udphdr *uh = tap_push_ip4h(ip4h, src, dst, l4len, IPPROTO_UDP);
+ char *data = tap_push_uh4(uh, src, sport, dst, dport, in, dlen);
+ memcpy(data, in, dlen);
tap_send_single(c, buf, dlen + (data - buf));
}
diff --git a/tap.h b/tap.h
index a476a12..0b3eb93 100644
--- a/tap.h
+++ b/tap.h
@@ -6,6 +6,8 @@
#ifndef TAP_H
#define TAP_H
+struct udphdr;
+
/**
* struct tap_hdr - tap backend specific headers
* @vnet_len: Frame length (for qemu socket transport)
@@ -42,6 +44,9 @@ static inline void tap_hdr_update(struct tap_hdr *thdr, size_t l2len)
thdr->vnet_len = htonl(l2len);
}
+void *tap_push_uh4(struct udphdr *uh, struct in_addr src, in_port_t sport,
+ struct in_addr dst, in_port_t dport,
+ const void *in, size_t dlen);
void tap_udp4_send(const struct ctx *c, struct in_addr src, in_port_t sport,
struct in_addr dst, in_port_t dport,
const void *in, size_t dlen);
--
2.48.1