Proof using.
induction l; intros; simpl in *.
- invcs H. intuition.
- break_match. invcs H.
intuition.
+ subst. intuition.
+ subst. simpl in *.
apply processPackets_correct with (p := p') in Heqp0; intuition.
+ subst. simpl in *.
apply processPackets_correct with (p := p) in Heqp0; intuition.
+ apply IHl with n0 l0 p p'; intuition.
Qed.
Set Regular Subst Tactic.

(* Specifications: *)
Lemma processPackets_seq_eq :
forall n l n' l' x y,
processPackets n l = (n', l') ->
In x l' ->
In y l' ->
tmNum (snd x) = tmNum (snd y) ->
x = y.