On 5/19/23 3:51 PM, Aditi Ghag wrote:
+static struct sock *bpf_iter_udp_batch(struct seq_file *seq)
+{
+ struct bpf_udp_iter_state *iter = seq->private;
+ struct udp_iter_state *state = &iter->state;
+ struct net *net = seq_file_net(seq);
+ struct udp_table *udptable;
+ unsigned int batch_sks = 0;
+ bool resized = false;
+ struct sock *sk;
+
+ /* The current batch is done, so advance the bucket. */
+ if (iter->st_bucket_done) {
+ state->bucket++;
+ iter->offset = 0;
+ }
+
+ udptable = udp_get_table_seq(seq, net);
+
+again:
+ /* New batch for the next bucket.
+ * Iterate over the hash table to find a bucket with sockets matching
+ * the iterator attributes, and return the first matching socket from
+ * the bucket. The remaining matched sockets from the bucket are batched
+ * before releasing the bucket lock. This allows BPF programs that are
+ * called in seq_show to acquire the bucket lock if needed.
+ */
+ iter->cur_sk = 0;
+ iter->end_sk = 0;
+ iter->st_bucket_done = false;
+ batch_sks = 0;
+
+ for (; state->bucket <= udptable->mask; state->bucket++) {
+ struct udp_hslot *hslot2 = &udptable->hash2[state->bucket];
+
+ if (hlist_empty(&hslot2->head)) {
+ iter->offset = 0;
+ continue;
+ }
+
+ spin_lock_bh(&hslot2->lock);
+ udp_portaddr_for_each_entry(sk, &hslot2->head) {
+ if (seq_sk_match(seq, sk)) {
+ /* Resume from the last iterated socket at the
+ * offset in the bucket before iterator was stopped.
+ */
+ if (iter->offset) {
+ --iter->offset;
Hi Aditi, I think this part has a bug.
When I run './test_progs -t bpf_iter/udp6' in a machine with some udp
so_reuseport sockets, this test is never finished.
A broken case I am seeing is when the bucket has >1 sockets and bpf_seq_read()
can only get one sk at a time before it calls bpf_iter_udp_seq_stop().
I did not try the change yet. However, from looking at the code where
iter->offset is changed, --iter->offset here is the most likely culprit and it
will make backward progress for the same bucket (state->bucket). Other places
touching iter->offset look fine.
It needs a local "int offset" variable for the zero test. Could you help to take
a look, add (or modify) a test and fix it?
The progs/bpf_iter_udp[46].c test can be used to reproduce. The test_udp[46] in
prog_tests/bpf_iter.c needs to be changed though to ensure there is multiple sk
in the same bucket. Probably a few so_reuseport sk should do.
Thanks.
+ continue;
+ }
+ if (iter->end_
