Reviewed-by: Eugene Crosser <crosser@xxxxxxxxxxx>
On 28/01/2022 00:06, Pablo Neira Ayuso wrote:
> If interface netlink dump is interrupted, then retry.
>
> Before this patch, the netlink socket is reopened to drop stale dump
> messages, instead empty the netlink queue and retry.
>
> Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
> ---
> v2: immediately return on non-eintr error (instead of breaking the loop),
> per Eugene Crosser.
>
> src/iface.c | 50 ++++++++++++++++++++++++++++++++++++++------------
> 1 file changed, 38 insertions(+), 12 deletions(-)
>
> diff --git a/src/iface.c b/src/iface.c
> index d0e1834ca82f..c0642e0cc397 100644
> --- a/src/iface.c
> +++ b/src/iface.c
> @@ -59,13 +59,13 @@ static int data_cb(const struct nlmsghdr *nlh, void *data)
> return MNL_CB_OK;
> }
>
> -void iface_cache_update(void)
> +static int iface_mnl_talk(struct mnl_socket *nl, uint32_t portid)
> {
> char buf[MNL_SOCKET_BUFFER_SIZE];
> - struct mnl_socket *nl;
> struct nlmsghdr *nlh;
> struct rtgenmsg *rt;
> - uint32_t seq, portid;
> + bool eintr = false;
> + uint32_t seq;
> int ret;
>
> nlh = mnl_nlmsg_put_header(buf);
> @@ -75,6 +75,38 @@ void iface_cache_update(void)
> rt = mnl_nlmsg_put_extra_header(nlh, sizeof(struct rtgenmsg));
> rt->rtgen_family = AF_PACKET;
>
> + if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0)
> + return -1;
> +
> + ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
> + while (ret > 0) {
> + ret = mnl_cb_run(buf, ret, seq, portid, data_cb, NULL);
> + if (ret == 0)
> + break;
> + if (ret < 0) {
> + if (errno != EINTR)
> + return ret;
> +
> + /* process all pending messages before reporting EINTR */
> + eintr = true;
> + }
> + ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
> + }
> +
> + if (eintr) {
> + ret = -1;
> + errno = EINTR;
> + }
> +
> + return ret;
> +}
> +
> +void iface_cache_update(void)
> +{
> + struct mnl_socket *nl;
> + uint32_t portid;
> + int ret;
> +
> nl = mnl_socket_open(NETLINK_ROUTE);
> if (nl == NULL)
> netlink_init_error();
> @@ -84,16 +116,10 @@ void iface_cache_update(void)
>
> portid = mnl_socket_get_portid(nl);
>
> - if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0)
> - netlink_init_error();
> + do {
> + ret = iface_mnl_talk(nl, portid);
> + } while (ret < 0 && errno == EINTR);
>
> - ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
> - while (ret > 0) {
> - ret = mnl_cb_run(buf, ret, seq, portid, data_cb, NULL);
> - if (ret <= MNL_CB_STOP)
> - break;
> - ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
> - }
> if (ret == -1)
> netlink_init_error();
>
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