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udp: Don't drop zero-length outbound UDP packets

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udp_tap_handler() currently skips outbound packets if they have a payload
length of zero.  This is not correct, since in a datagram protocol zero
length packets still have meaning.

Adjust this to correctly forward the zero-length packets by using a msghdr
with msg_iovlen == 0.

Bugzilla: https://bugs.passt.top/show_bug.cgi?id=19

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
David Gibson 2022-09-13 16:37:44 +10:00 committed by Stefano Brivio
parent 484652c632
commit af9c98af5f
1 changed files with 10 additions and 7 deletions
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17
udp.c
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@ -1075,17 +1075,20 @@ int udp_tap_handler(struct ctx *c, int af, const void *addr,
uh_send = packet_get(p, i, 0, sizeof(*uh), &len); uh_send = packet_get(p, i, 0, sizeof(*uh), &len);
if (!uh_send) if (!uh_send)
return p->count; return p->count;
if (!len)
continue;
m[i].iov_base = (char *)(uh_send + 1);
m[i].iov_len = len;
mm[i].msg_hdr.msg_name = sa; mm[i].msg_hdr.msg_name = sa;
mm[i].msg_hdr.msg_namelen = sl; mm[i].msg_hdr.msg_namelen = sl;
mm[i].msg_hdr.msg_iov = m + i; if (len) {
mm[i].msg_hdr.msg_iovlen = 1; m[i].iov_base = (char *)(uh_send + 1);
m[i].iov_len = len;
mm[i].msg_hdr.msg_iov = m + i;
mm[i].msg_hdr.msg_iovlen = 1;
} else {
mm[i].msg_hdr.msg_iov = NULL;
mm[i].msg_hdr.msg_iovlen = 0;
}
mm[i].msg_hdr.msg_control = NULL; mm[i].msg_hdr.msg_control = NULL;
mm[i].msg_hdr.msg_controllen = 0; mm[i].msg_hdr.msg_controllen = 0;