We recently enabled the IP_PKTINFO / IPV6_RECVPKTINFO socket options on our
UDP sockets. This lets us obtain and properly handle the specific local
address used when we're "listening" with a socket on 0.0.0.0 or ::.
However, the PKTINFO cmsgs this option generates appear on error queue
messages as well as regular datagrams. udp_sock_recverr() doesn't expect
this and so flags an unrecoverable error when it can't parse the control
message.
Correct this by adding space in udp_sock_recverr()s control buffer for the
additional PKTINFO data, and scan through all cmsgs for the RECVERR, rather
than only looking at the first one.
Link: https://bugs.passt.top/show_bug.cgi?id=99
Fixes: f4b0dd8b06 ("udp: Use PKTINFO cmsgs to get destination address..")
Reported-by: Stefano Brivio
Signed-off-by: David Gibson
---
udp.c | 30 +++++++++++++++++-------------
1 file changed, 17 insertions(+), 13 deletions(-)
diff --git a/udp.c b/udp.c
index 40af7dfc..f5fb98c2 100644
--- a/udp.c
+++ b/udp.c
@@ -155,6 +155,10 @@ __attribute__ ((aligned(32)))
#endif
udp_meta[UDP_MAX_FRAMES];
+#define PKTINFO_SPACE \
+ MAX(CMSG_SPACE(sizeof(struct in_pktinfo)), \
+ CMSG_SPACE(sizeof(struct in6_pktinfo)))
+
/**
* enum udp_iov_idx - Indices for the buffers making up a single UDP frame
* @UDP_IOV_TAP tap specific header
@@ -476,10 +480,10 @@ static int udp_sock_recverr(const struct ctx *c, union epoll_ref ref)
struct sock_extended_err ee;
union sockaddr_inany saddr;
};
- const struct errhdr *eh;
- const struct cmsghdr *hdr;
- char buf[CMSG_SPACE(sizeof(struct errhdr))];
+ char buf[PKTINFO_SPACE + CMSG_SPACE(sizeof(struct errhdr))];
char data[ICMP6_MAX_DLEN];
+ const struct errhdr *eh;
+ struct cmsghdr *hdr;
int s = ref.fd;
struct iovec iov = {
.iov_base = data,
@@ -507,12 +511,16 @@ static int udp_sock_recverr(const struct ctx *c, union epoll_ref ref)
return -1;
}
- hdr = CMSG_FIRSTHDR(&mh);
- if (!((hdr->cmsg_level == IPPROTO_IP &&
- hdr->cmsg_type == IP_RECVERR) ||
- (hdr->cmsg_level == IPPROTO_IPV6 &&
- hdr->cmsg_type == IPV6_RECVERR))) {
- err("Unexpected cmsg reading error queue");
+ for (hdr = CMSG_FIRSTHDR(&mh); hdr; hdr = CMSG_NXTHDR(&mh, hdr)) {
+ if ((hdr->cmsg_level == IPPROTO_IP &&
+ hdr->cmsg_type == IP_RECVERR) ||
+ (hdr->cmsg_level == IPPROTO_IPV6 &&
+ hdr->cmsg_type == IPV6_RECVERR))
+ break;
+ }
+
+ if (!hdr) {
+ err("Missing RECVERR cmsg in error queue");
return -1;
}
@@ -587,10 +595,6 @@ static int udp_sock_errs(const struct ctx *c, union epoll_ref ref)
return n_err;
}
-#define PKTINFO_SPACE \
- MAX(CMSG_SPACE(sizeof(struct in_pktinfo)), \
- CMSG_SPACE(sizeof(struct in6_pktinfo)))
-
/**
* udp_peek_addr() - Get source address for next packet
* @s: Socket to get information from
--
2.49.0