Currently we open code parsing the control message for IP_PKTINFO in
udp_peek_addr(). We have an upcoming case where we want to parse PKTINFO
in another place, so split this out into a helper function.
While we're there, make the parsing a bit more robust: scan all cmsgs to
look for the one we want, rather than assuming there's only one.
Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
---
udp.c | 52 ++++++++++++++++++++++++++++++++++++----------------
1 file changed, 36 insertions(+), 16 deletions(-)
diff --git a/udp.c b/udp.c
index 0bec499d..352ab83b 100644
--- a/udp.c
+++ b/udp.c
@@ -464,6 +464,41 @@ static void udp_send_tap_icmp6(const struct ctx *c,
tap_icmp6_send(c, saddr, eaddr, &msg, msglen);
}
+/**
+ * udp_pktinfo() - Retreive packet destination address from cmsg
+ * @msg: msghdr into which message has been received
+ * @dst: (Local) destination address of message in @mh (output)
+ *
+ * Return: 0 on success, -1 if the information was missing (@dst is set to
+ * inany_any6).
+ */
+static int udp_pktinfo(struct msghdr *msg, union inany_addr *dst)
+{
+ struct cmsghdr *hdr;
+
+ for (hdr = CMSG_FIRSTHDR(msg); hdr; hdr = CMSG_NXTHDR(msg, hdr)) {
+ if (hdr->cmsg_level == IPPROTO_IP &&
+ hdr->cmsg_type == IP_PKTINFO) {
+ const struct in_pktinfo *i4 = (void *)CMSG_DATA(hdr);
+
+ *dst = inany_from_v4(i4->ipi_addr);
+ return 0;
+ }
+
+ if (hdr->cmsg_level == IPPROTO_IPV6 &&
+ hdr->cmsg_type == IPV6_PKTINFO) {
+ const struct in6_pktinfo *i6 = (void *)CMSG_DATA(hdr);
+
+ dst->a6 = i6->ipi6_addr;
+ return 0;
+ }
+ }
+
+ err("Missing PKTINFO cmsg on datagram");
+ *dst = inany_any6;
+ return -1;
+}
+
/**
* udp_sock_recverr() - Receive and clear an error from a socket
* @c: Execution context
@@ -607,7 +642,6 @@ static int udp_peek_addr(int s, union sockaddr_inany *src,
union inany_addr *dst)
{
char sastr[SOCKADDR_STRLEN], dstr[INANY_ADDRSTRLEN];
- const struct cmsghdr *hdr;
char cmsg[PKTINFO_SPACE];
struct msghdr msg = {
.msg_name = src,
@@ -624,21 +658,7 @@ static int udp_peek_addr(int s, union sockaddr_inany *src,
return -errno;
}
- hdr = CMSG_FIRSTHDR(&msg);
- if (hdr && hdr->cmsg_level == IPPROTO_IP &&
- hdr->cmsg_type == IP_PKTINFO) {
- const struct in_pktinfo *info4 = (void *)CMSG_DATA(hdr);
-
- *dst = inany_from_v4(info4->ipi_addr);
- } else if (hdr && hdr->cmsg_level == IPPROTO_IPV6 &&
- hdr->cmsg_type == IPV6_PKTINFO) {
- const struct in6_pktinfo *info6 = (void *)CMSG_DATA(hdr);
-
- dst->a6 = info6->ipi6_addr;
- } else {
- debug("Unexpected cmsg on UDP datagram");
- *dst = inany_any6;
- }
+ udp_pktinfo(&msg, dst);
trace("Peeked UDP datagram: %s -> %s",
sockaddr_ntop(src, sastr, sizeof(sastr)),
--
2.49.0